Control of Air Pollution From New Motor Vehicles and New Motor Vehicle Engines; Regulations Requiring Onboard Diagnostic Systems on 2010 and Later Heavy-Duty Engines Used in Highway Applications Over 14,000 Pounds; Revisions to Onboard Diagnostic Requirements for Diesel Highway Heavy-Duty Vehicles Under 14,000 Pounds

Federal RegisterJan 24, 2007

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ENVIRONMENTAL PROTECTION AGENCY

40 CFR Part 86

[OAR-2005-0047; FRL-8256-9]

RIN 2060-AL92

Control of Air Pollution From New Motor Vehicles and New Motor Vehicle Engines; Regulations Requiring Onboard Diagnostic Systems on 2010 and Later Heavy-Duty Engines Used in Highway Applications Over 14,000 Pounds; Revisions to Onboard Diagnostic Requirements for Diesel Highway Heavy-Duty Vehicles Under 14,000 Pounds

AGENCY:

Environmental Protection Agency (EPA).

ACTION:

Notice of proposed rulemaking.

SUMMARY:

In 2001, EPA finalized a new, major program for highway heavy-duty engines. That program, the Clean Diesel Trucks and Buses program, will result in the introduction of advanced emissions control systems such as catalyzed diesel particulate filters (DPF) and catalysts capable of reducing harmful nitrogen oxide (NO

) emissions. This proposal would require that these advanced emissions control systems be monitored for malfunctions via an onboard diagnostic system (OBD), similar to those systems that have been required on passenger cars since the mid-1990s. This proposal would require manufacturers to install OBD systems that monitor the functioning of emission control components and alert the vehicle operator to any detected need for emission related repair. This proposal would also require that manufacturers make available to the service and repair industry information necessary to perform repair and maintenance service on OBD systems and other emission related engine components. Lastly, this proposal would revise certain existing OBD requirements for diesel engines used in heavy-duty vehicles under 14,000 pounds.

DATES:

If we do not receive a request for a public hearing, written comments are due March 26, 2007. Requests for a public hearing must be received by February 8, 2007. If we do receive a request for a public hearing, we will publish a notice in the

Federal Register

and on the Web at

http://www.epa.gov/obd/regtech/heavy.htm

containing details regarding the location, date, and time of the public hearing. In that case, the public comment period would close 30 days after the public hearing. Under the Paperwork Reduction Act, comments on the information collection provisions must be received by OMB on or before February 23, 2007.

ADDRESSES:

Submit your comments, identified by Docket ID No. EPA-HQ-OAR-2005-0047, by one of the following methods:

•

http://www.regulations.gov:

Follow the on-line instructions for submitting comments.

•

Mail:

Onboard Diagnostic (OBD) Systems on 2010 and Later Heavy-Duty Highway Vehicles and Engines, Environmental Protection Agency, Mailcode: 6102T, 1200 Pennsylvania Ave., NW., Washington, DC, 20460, Attention Docket ID No. EPA-HQ-OAR-2005-0047. In addition, please mail a copy of your comments on the information collection provisions to the Office of Information and Regulatory Affairs, Office of Management and Budget (OMB), Attn: Desk Officer for EPA, 725 17th St. NW., Washington, DC 20503.

Instructions:

Direct your comments to Docket ID No. EPA-HQ-OAR-2005-0047. EPA's policy is that all comments received will be included in the public docket without change and may be made available online at

http://www.regulations.gov,

including any personal information provided, unless the comment includes information claimed to be Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Do not submit information that you consider to be CBI or otherwise protected through

http://www.regulations.gov

or e-mail. The

http://www.regulations.gov

Web site is an “anonymous access” system, which means EPA will not know your identity or contact information unless you provide it in the body of your comment. If you send an e-mail comment directly to EPA without going through

http://www.regulations.gov

your e-mail address will be automatically captured and included as part of the comment that is placed in the public docket and made available on the Internet. If you submit an electronic comment, EPA recommends that you include your name and other contact information in the body of your comment and with any disk or CD-ROM you submit. If EPA cannot read your comment due to technical difficulties and cannot contact you for clarification, EPA may not be able to consider your comment. Electronic files should avoid the use of special characters, any form of encryption, and be free of any defects or viruses.

Docket:

All documents in the docket are listed in the

http://www.regulations.gov

index. Although listed in the index, some information is not publicly available, e.g., CBI or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, will be publicly available only in hard copy. Publicly available docket materials are available either electronically in

http://www.regulations.gov

or in hard copy at the Air Docket, EPA/DC, EPA West, Room B102, 1301 Constitution Ave., NW., Washington, DC. The Public Reading Room is open from 8:30 a.m. to 4:30 p.m., Monday through Friday, excluding legal holidays. The telephone number for the Public Reading Room is (202) 566-1744, and the telephone number for the Air Docket is (202) 566-1742.

Note:

The EPA Docket Center suffered damage due to flooding during the last week of June 2006. The Docket Center is continuing to operate. However, during the cleanup, there will be temporary changes to Docket Center telephone numbers, addresses, and hours of operation for people who wish to make hand deliveries or visit the Public Reading Room to view documents. Consult EPA's

Federal Register

notice at 71 FR 38147 (July 5, 2006) or the EPA Web site at

http://www.epa.gov/epahome/dockets.htm

for current information on docket operations, locations and telephone numbers. The Docket Center's mailing address for U.S. mail and the procedure for submitting comments to

www.regulations.gov

are not affected by the flooding and will remain the same.

FOR FURTHER INFORMATION CONTACT:

U.S. EPA, National Vehicle and Fuel Emissions Laboratory, Assessment and Standards Division, 2000 Traverwood Drive, Ann Arbor, MI 48105; telephone (734) 214-4405, fax (734) 214-4816, email

sherwood.todd@epa.gov.

SUPPLEMENTARY INFORMATION:

Regulated Entities

This action will affect you if you produce or import new heavy-duty engines which are intended for use in highway vehicles such as trucks and buses, or produce or import such highway vehicles, or convert heavy-duty vehicles or heavy-duty engines used in highway vehicles to use alternative fuels.

The following table gives some examples of entities that may have to follow the regulations. But because these are only examples, you should carefully examine the regulations in 40 CFR part 86. If you have questions, call the person listed in the

FOR FURTHER INFORMATION CONTACT

section of this preamble:

Category

NAICS Codes

SIC Codes

Examples of potentially regulated

entities

Industry

336111

336112

336120

3711

Motor Vehicle Manufacturers; Engine and Truck Manufacturers.

Industry

811112

811198

541514

7533

7549

8742

Commercial Importers of Vehicles and Vehicle Components.

Industry

336111

3592

Alternative fuel vehicle converters.

336312

3714

422720

5172

454312

5984

811198

7549

541514

8742

541690

8931

North American Industry Classification Systems (NAICS).

Standard Industrial Classification (SIC) system code.

What Should I Consider as I Prepare My Comments for EPA?

Submitting CBI.

Do not submit this information to EPA through

www.regulations.gov

or e-mail. Clearly mark the part or all of the information that you claim to be CBI. For CBI information in a disk or CD ROM that you mail to EPA, mark the outside of the disk or CD ROM as CBI and then identify electronically within the disk or CD ROM the specific information that is claimed as CBI). In addition to one complete version of the comment that includes information claimed as CBI, a copy of the comment that does not contain the information claimed as CBI must be submitted for inclusion in the public docket. Information so marked will not be disclosed except in accordance with procedures set forth in 40 CFR part 2.

Tips for Preparing Your Comments.

When submitting comments, remember to:

• Identify the rulemaking by docket number and other identifying information (subject heading,

Federal Register

date and page number).

• Follow directions—The agency may ask you to respond to specific questions or organize comments by referencing a Code of Federal Regulations (CFR) part or section number.

• Explain why you agree or disagree; suggest alternatives and substitute language for your requested changes.

• Describe any assumptions and provide any technical information and/or data that you used.

• If you estimate potential costs or burdens, explain how you arrived at your estimate in sufficient detail to allow for it to be reproduced.

• Provide specific examples to illustrate your concerns, and suggest alternatives.

• Explain your views as clearly as possible, avoiding the use of profanity or personal threats.

• Make sure to submit your comments by the comment period deadline identified.

Outline of this Preamble

I. Overview

A. Background

B. What Is EPA Proposing?

1. OBD Requirements for Engines Used in Highway Vehicles Over 14,000 Pounds GVWR

2. Requirements That Service Information Be Made Available

3. OBD Requirements for Diesel Heavy-Duty Vehicles and Engines Used in Vehicles Under 14,000 Pounds

C. Why Is EPA Making This Proposal?

1. Highway Engines and Vehicles Contribute to Serious Air Pollution Problems

2. Emissions Control of Highway Engines and Vehicles Depends on Properly Operating Emissions Control Systems

3. Basis for Action Under the Clean Air Act

D. How Has EPA Chosen the Level of the Proposed Emissions Thresholds?

E. World Wide Harmonized OBD (WWH-OBD)

F. Onboard Diagnostics for Diesel Engines Used in Nonroad Land-Based Equipment

1. What Is the Baseline Nonroad OBD System?

2. What Is The Appropriate Level of OBD Monitoring for Nonroad Diesel Engines?

3. What Should the OBD Standardization Features Be?

4. What Are the Prospects and/or Desires for International Harmonization of Nonroad OBD?

II. What Are the Proposed OBD Requirements and When Would They Be Implemented?

A. General OBD System Requirements

1. The OBD System

2. Malfunction Indicator Light (MIL) and Diagnostic Trouble Codes (DTC)

3. Monitoring Conditions

4. Determining the Proper OBD Malfunction Criteria

B. Monitoring Requirements and Timelines for Diesel-Fueled/Compression-Ignition Engines

1. Fuel System Monitoring

2. Engine Misfire Monitoring

3. Exhaust Gas Recirculation (EGR) System Monitoring

4. Turbo Boost Control System Monitoring

5. Non-Methane Hydrocarbon (NMHC) Converting Catalyst Monitoring

6. Selective Catalytic Reduction (SCR) and Lean NO

Catalyst Monitoring

7. NO

Adsorber System Monitoring

8. Diesel Particulate Filter (DPF) System Monitoring

9. Exhaust Gas Sensor Monitoring

C. Monitoring Requirements and Timelines for Gasoline/Spark-Ignition Engines

1. Fuel System Monitoring

2. Engine Misfire Monitoring

3. Exhaust Gas Recirculation (EGR) Monitoring

4. Cold Start Emission Reduction Strategy Monitoring

5. Secondary Air System Monitoring

6. Catalytic Converter Monitoring

7. Evaporative Emission Control System Monitoring

8. Exhaust Gas Sensor Monitoring

D. Monitoring Requirements and Timelines for Other Diesel and Gasoline Systems

1. Variable Valve Timing and/or Control (VVT) System Monitoring

2. Engine Cooling System Monitoring

3. Crankcase Ventilation System Monitoring

4. Comprehensive Component Monitors

5. Other Emissions Control System Monitoring

6. Exceptions to Monitoring Requirements

E. A Standardized Method To Measure Real World Monitoring Performance

1. Description of Software Counters To Track Real World Performance

2. Proposed Performance Tracking Requirements

F. Standardization Requirements

1. Reference Documents

2. Diagnostic Connector Requirements

3. Communications to a Scan Tool

4. Required Emissions Related Functions

5. In-Use Performance Ratio Tracking Requirements

6. Exceptions to Standardization Requirements

G. Implementation Schedule, In-Use Liability, and In-Use Enforcement

1. Implementation Schedule and In-Use Liability Provisions

2. In-Use Enforcement

H. Proposed Changes to the Existing 8,500 to 14,000 Pound Diesel OBD Requirements

1. Selective Catalytic Reduction and Lean NO

Catalyst Monitoring

2. NO

Adsorber System Monitoring

3. Diesel Particulate Filter System Monitoring

4. NMHC Converting Catalyst Monitoring

5. Other Monitors

6. CARB OBDII Compliance Option and Deficiencies

I. How Do the Proposed Requirements Compare to California's?

III. Are the Proposed Monitoring Requirements Feasible?

A. Feasibility of the Monitoring Requirements for Diesel/Compression-Ignition Engines

1. Fuel System Monitoring

2. Engine Misfire Monitoring

3. Exhaust Gas Recirculation (EGR) Monitoring

4. Turbo Boost Control System Monitoring

5. Non-Methane Hydrocarbon (NMHC) Converting Catalyst Monitoring

6. Selective Catalytic Reduction (SCR) and NO

Conversion Catalyst Monitoring

7. NO

Adsorber Monitoring

8. Diesel Particulate Filter (DPF) Monitoring

9. Exhaust Gas Sensor Monitoring

B. Feasibility of the Monitoring Requirements for Gasoline/Spark-Ignition Engines

1. Fuel System Monitoring

2. Engine Misfire Monitoring

3. Exhaust Gas Recirculation (EGR) Monitoring

4. Cold Start Emission Reduction Strategy Monitoring

5. Secondary Air System Monitoring

6. Catalytic Converter Monitoring

7. Evaporative System Monitoring

8. Exhaust Gas Sensor Monitoring

C. Feasibility of the Monitoring Requirements for Other Diesel and Gasoline Systems

1. Variable Valve Timing and/or Control (VVT) System Monitoring

2. Engine Cooling System Monitoring

3. Crankcase Ventilation System Monitoring

4. Comprehensive Component Monitoring

IV. What Are the Service Information Availability Requirements?

A. What Is the Important Background Information for the Proposed Service Information Provisions?

B. How Do the Below 14,000 Pound and Above 14,000 Pounds Aftermarket Service Industry Compare?

C. What Provisions Are Being Proposed for Service Information Availability?

1. What Information Is Proposed To Be Made Available by OEMs?

2. What Are the Proposed Requirements for Web-Based Delivery of the Required Information?

3. What Provisions Are Being Proposed for Service Information for Third Party Information Providers?

4. What Requirements Are Being Proposed for the Availability of Training Information?

5. What Requirements Are Being Proposed for Reprogramming of Vehicles?

6. What Requirements Are Being Proposed for the Availability of Enhanced Information for Scan Tools for Equipment and Tool Companies?

7. What Requirements Are Being Proposed for the Availability of OEM—Specific Diagnostic Scan Tools and Other Special Tools?

8. Which Reference Materials Are Being Proposed for Incorporation by Reference?

V. What Are the Emissions Reductions Associated With the Proposed OBD Requirements?

VI. What Are the Costs Associated With the Proposed OBD Requirements?

A. Variable Costs for Engines Used in Vehicles Over 14,000 Pounds

B. Fixed Costs for Engines Used in Vehicles Over 14,000 Pounds

C. Total Costs for Engines Used in Vehicles Over 14,000 Pounds

D. Costs for Diesel Heavy-Duty Vehicles and Engines Used in Heavy-Duty Vehicles Under 14,000 Pounds

VII. What are the Updated Annual Costs and Costs per Ton Associated With the 2007/2010 Heavy-Duty Highway Program?

A. Updated 2007 Heavy-Duty Highway Rule Costs Including OBD

B. Updated 2007 Heavy-Duty Highway Rule Costs Per Ton Including OBD

VIII. What Are the Requirements for Engine Manufacturers?

A. Documentation Requirements

B. Catalyst Aging Procedures

C. Demonstration Testing

1. Selection of Test Engines

2. Required Testing

3. Testing Protocol

4. Evaluation Protocol

5. Confirmatory Testing

D. Deficiencies

E. Production Evaluation Testing

1. Verification of Standardization Requirements

2. Verification of Monitoring Requirements

3. Verification of In-Use Monitoring Performance Ratios

IX. What Are the Issues Concerning Inspection and Maintenance Programs?

A. Current Heavy-Duty I/M Programs

B. Challenges for Heavy-Duty I/M

C. Heavy-Duty OBD and I/M

X. Statutory and Executive Order Reviews

A. Executive Order 12866: Regulatory Planning and Review

B. Paperwork Reduction Act

C. Regulatory Flexibility Act (RFA), as Amended by the Small Business Regulatory Enforcement Fairness Act of 1996 (SBREFA), 5 U.S.C. 601 et. seq.

D. Unfunded Mandates Reform Act

E. Executive Order 13132: Federalism

F. Executive Order 13175: Consultation and Coordination With Indian Tribal Governments

G. Executive Order 13045: Protection of Children From Environmental Health and Safety Risks

H. Executive Order 13211: Actions That Significantly Affect Energy Supply, Distribution, or Use

I. National Technology Transfer Advancement Act

XI. Statutory Provisions and Legal Authority

I. Overview

A. Background

Section 202(m) of the CAA, 42 U.S.C. 7521(m), directs EPA to promulgate regulations requiring 1994 and later model year light-duty vehicles (LDVs) and light-duty trucks (LDTs) to contain an OBD system that monitors emission-related components for malfunctions or deterioration “which could cause or result in failure of the vehicles to comply with emission standards established” for such vehicles. Section 202(m) also states that, “The Administrator may, in the Administrator's discretion, promulgate regulations requiring manufacturers to install such onboard diagnostic systems on heavy-duty vehicles and engines.”

On February 19, 1993, we published a final rule requiring manufacturers of light-duty applications to install such OBD systems on their vehicles beginning with the 1994 model year (58 FR 9468). The OBD systems must monitor emission control components for any malfunction or deterioration that could cause exceedance of certain emission thresholds. The regulation also required that the driver be notified of any need for repair via a dashboard light, or malfunction indicator light (MIL), when the diagnostic system detected a problem. We also allowed optional compliance with California's second phase OBD requirements, referred to as OBDII (13 CCR 1968.1), for purposes of satisfying the EPA OBD requirements. Since publishing the 1993 OBD final rule, EPA has made several revisions to the OBD requirements, most of which served to align the EPA OBD requirements with revisions to the California OBDII requirements (13 CCR 1968.2).

On August 9, 1995, EPA published a final rulemaking that set forth service information regulations for light-duty vehicles and light-duty trucks (60 FR 40474). These regulations, in part, required each Original Equipment Manufacturer (OEM) to do the following: (1) List all of its emission-related service and repair information on a Web site called FedWorld (including the cost of each item and where it could be purchased); (2) either provide enhanced information to equipment and tool companies or make its OEM-specific diagnostic tool available for purchase by aftermarket technicians, and (3) make reprogramming capability available to independent service and repair professionals if its franchised dealerships had such capability. These requirements are intended to ensure that aftermarket service and repair facilities

have access to the same emission-related service information, in the same or similar manner, as that provided by OEMs to their franchised dealerships. These service information availability requirements have been revised since that first final rule in response to changing technology among other reasons. (68 FR 38428)

In October of 2000, we published a final rule requiring OBD systems on heavy-duty vehicles and engines up to 14,000 pounds GVWR (65 FR 59896). In that rule, we expressed our intention of developing OBD requirements in a future rule for vehicles and engines used in vehicles over 14,000 pounds. We expressed this same intention in our 2007HD highway final rule (66 FR 5002) which established new heavy-duty highway emissions standards for 2007 and later model year engines. In June of 2003, we published a final rule extending service information availability requirements to heavy-duty vehicles and engines weighing up to 14,000 pounds GVWR. We declined extending these requirements to engines above 14,000 pounds GVWR at least until such engines are subject to OBD requirements.

On January 18, 2001, EPA established a comprehensive national control program—the Clean Diesel Truck and Bus program—that regulates the heavy-duty vehicle and its fuel as a single system. (66 FR 5002) As part of this program, new emission standards will begin to take effect in model year 2007 and will apply to heavy-duty highway engines and vehicles. These standards are based on the use of high-efficiency catalytic exhaust emission control devices or comparably effective advanced technologies. Because these devices are damaged by sulfur, the regulation also requires the level of sulfur in highway diesel fuel be reduced by 97 percent.

Note that the 2007HD highway rule contained new emissions standards for gasoline engines as well as diesel engines.

Today's action proposes new OBD requirements for highway engines used in vehicles greater than 14,000 pounds. Today's action also proposes new availability requirements for emission-related service information that will make this information more widely available to the industry servicing vehicles over 14,000 pounds.

In addition to these proposed requirements and changes, we are seeking comment on possible future regulations that would require OBD systems on heavy-duty diesel engines used in nonroad equipment. Diesel engines used in nonroad equipment are, like highway engines, a major source of NO

and particulate matter (PM) emissions, and the diesel engines used in nonroad equipment are essentially the same as those used in heavy-duty highway trucks. Further, new regulations applicable to nonroad diesel engines will result in the introduction of advanced emissions control systems like those expected for highway diesel engines. (69 FR 38958) Therefore, having OBD systems and OBD regulations for nonroad engines seems to be a natural progression from the proposed requirements for heavy-duty highway engines. We discuss this issue in greater detail in section I of this preamble with the goal of soliciting public comment regarding how we should proceed with respect to nonroad OBD.

B. What Is EPA Proposing?

1. OBD Requirements for Engines Used in Highway Vehicles Over 14,000 Pounds GVWR

We believe that OBD requirements should be extended to include over 14,000 pound heavy-duty vehicles and engines for many reasons. In the past, heavy-duty diesel engines have relied primarily on in-cylinder modifications to meet emission standards. For example, emission standards have been met through changes in fuel timing, piston design, combustion chamber design, charge air cooling, use of four valves per cylinder rather than two valves, and piston ring pack design and location improvements. In contrast, the 2004 and 2007 emission standards represent a different sort of technological challenge that are being met with the addition of exhaust gas recirculation (EGR) systems and the addition of exhaust aftertreatment devices such as diesel particulate filters (DPF), sometimes called PM traps, and NO

catalysts. Such “add on” devices can experience deterioration and malfunction that, unlike the engine design elements listed earlier, may go unnoticed by the driver. Because deterioration and malfunction of these devices can go unnoticed by the driver, and because their primary purpose is emissions control, and because the level of emission control is on the order of 50 to 99 percent, some form of diagnosis and malfunction detection is crucial. We believe that such detection can be effectively achieved by employing a well designed OBD system.

The same is true for gasoline heavy-duty vehicles and engines. While emission control is managed with both engine design elements and aftertreatment devices, the catalytic converter is the primary emission control feature accounting for over 95 percent of the emission control. We believe that monitoring the emission control system for proper operation is critical to ensure that new vehicles and engines certified to the very low emission standards set in recent years continue to meet those standards throughout their full useful life.

Further, the industry trend is clearly toward increasing use of computer and electronic controls for both engine and powertrain management, and for emission control. In fact, the heavy-duty industry has already gone a long way, absent any government regulation, to standardize computer communication protocols.

Computer and electronic control systems, as opposed to mechanical systems, provide improvements in many areas including, but not limited to, improved precision and control, reduced weight, and lower cost. However, electronic and computer controls also create increased difficulty in diagnosing and repairing the malfunctions that inevitably occur in any engine or powertrain system. Today's proposed OBD requirements would build on the efforts already undertaken by the industry to ensure that key emissions related components will be monitored in future heavy-duty vehicles and engines and that the diagnosis and repair of those components will be as efficient and cost effective as possible.

See “On-Board Diagnostics, A Heavy-Duty Perspective,” SAE 951947; “Recommended Practice for a Serial Control and Communications Vehicle Network,” SAE J1939 which may be obtained from Society of Automotive Engineers International, 400 Commonwealth Dr., Warrendale, PA, 15096-0001; and “Road Vehicles-Diagnostics on Controller Area Network (CAN)—Part 4: Requirements for emission-related systems,” ISO 15765-4:2001 which may be obtained from the International Organization for Standardization, Case Postale 56, CH-1211 Geneva 20, Switzerland.

Lastly, heavy-duty engines and, in particular, diesel engines tend to have very long useful lives. With age comes deterioration and a tendency toward increasing emissions. With the OBD systems proposed today, we expect that these engines will continue to be properly maintained and therefore will continue to emit at low emissions levels even after accumulating hundreds of thousands and even a million miles.

For the reasons laid out above, most manufacturers of vehicles, trucks, and engines have incorporated some type of OBD system into their products that are capable of identifying when certain types of malfunctions occur, and in what systems. In the heavy-duty industry, those OBD systems traditionally have been geared toward

detecting malfunctions causing drivability and/or fuel economy related problems. Without specific requirements for manufacturers to include OBD mechanisms to detect emission-related problems, those types of malfunctions that could result in high emissions without a corresponding adverse drivability or fuel economy impact could go unnoticed by both the driver and the repair technician. The resulting increase in emissions and detrimental impact on air quality could be avoided by incorporating an OBD system capable of detecting emission control system malfunctions.

2. Requirements That Service Information Be Made Available

We are proposing that makers of engines that go into vehicles over 14,000 pounds make available to any person engaged in repair or service all information necessary to make use of the OBD systems and for making emission-related repairs, including any emissions-related information that is provided by the OEM to franchised dealers. This information includes, but is not limited to, manuals, technical service bulletins (TSBs), a general description of the operation of each OBD monitor, etc. We discuss the proposed requirements further in section IV of this preamble.

The proposed requirements are similar to those required currently for all 1996 and newer light-duty vehicles and light-duty trucks and 2005 and newer heavy-duty applications up to 14,000 pounds. While EPA understands that there may be some differences between aftermarket service for the under 14,000 pound and over 14,000 pound applications, we believe that any such differences would not substantially affect the implementation of such requirements and that, therefore, it is reasonable to use EPA's existing service information regulations as a basis for proposing service information requirements for the over 14,000 pound arena. See section IV for a complete discussion of the service information provisions being proposed for the availability of over 14,000 pound service information.

Note that information for making emission-related repairs does not include information used to design and manufacture parts, but it may include OEM changes to internal calibrations and other indirect information, as discussed in section IV.

3. OBD Requirements for Diesel Heavy-Duty Vehicles and Engines Used in Vehicles Under 14,000 Pounds

We are also proposing some changes to the existing diesel OBD requirements for heavy-duty applications under 14,000 pounds (i.e., 8,500 to 14,000 pounds). Some of these changes are being proposed for the 2007 and later model years (i.e., for immediate implementation) because we believe that some of the requirements that we currently have in place for 8,500 to 14,000 pound applications cannot be met by diesels without granting widespread deficiencies to industry. Other changes are being proposed for the 2010 and later model years since they represent an increase in the stringency of our current OBD requirements and, therefore, some leadtime is necessary for manufacturers to comply. All of the changes being proposed for 8,500 to 14,000 pound diesel applications would result in OBD emissions thresholds identical, for all practical purposes, to the OBD thresholds being proposed for over 14,000 pound applications.

C. Why Is EPA Making This Proposal?

1. Highway Engines and Vehicles Contribute to Serious Air Pollution Problems

The pollution emitted by heavy-duty highway engines contributes greatly to our nation's continuing air quality problems. Our 2007HD highway rule was designed to address these serious air quality problems. These problems include premature mortality, aggravation of respiratory and cardiovascular disease, aggravation of existing asthma, acute respiratory symptoms, chronic bronchitis, and decreased lung function. Numerous studies also link diesel exhaust to increased incidence of lung cancer. We believe that diesel exhaust is likely to be carcinogenic to humans by inhalation and that this cancer hazard exists for occupational and environmental levels of exposure.

Our 2007HD highway rule will regulate the heavy-duty vehicle and its fuel as a single system. As part of this program, new emission standards will begin to take effect in model year 2007 and phase-in through model year 2010, and will apply to heavy-duty highway engines and vehicles. These standards are based on the use of high-efficiency catalytic exhaust emission control devices or comparably effective advanced technologies and a cap on the allowable sulfur content in both diesel fuel and gasoline.

In the 2007HD highway final rule, we estimated that, by 2007, heavy-duty trucks and buses would account for about 28 percent of nitrogen oxides emissions and 20 percent of particulate matter emissions from mobile sources. In some urban areas, the contribution is even greater. The 2007HD highway program will reduce particulate matter and oxides of nitrogen emissions from heavy-duty engines by 90 percent and 95 percent below current standard levels, respectively. In order to meet these more stringent standards for diesel engines, the program calls for a 97 percent reduction in the sulfur content of diesel fuel. As a result, diesel vehicles will achieve gasoline-like exhaust emission levels. We have also established more stringent standards for heavy-duty gasoline vehicles, based in part on the use of the low sulfur gasoline that will be available when the standards go into effect.

2. Emissions Control of Highway Engines and Vehicles Depends on Properly Operating Emissions Control Systems

The emissions reductions and resulting health and welfare benefits of the 2007HD highway program will be dramatic when fully implemented. By 2030, the program will reduce annual emissions of nitrogen oxides, nonmethane hydrocarbons, and particulate matter by a projected 2.6 million, 115,000 and 109,000 tons, respectively. However, to realize those large emission reductions and health benefits, the emission control systems on heavy-duty highway engines and vehicles must continue to provide the 90 to 95 percent emission control effectiveness throughout their operating life. Today's proposed OBD requirements will help to ensure that emission control systems continue to operate properly by detecting when those systems malfunction, by then notifying the driver that a problem exists that requires service and, lastly, by informing the service technician what the problem is so that it can be properly repaired.

3. Basis for Action Under the Clean Air Act

202(m) also states that, “The Administrator may, in the Administrator's discretion, promulgate regulations requiring manufacturers to install such onboard diagnostic systems on heavy-duty vehicles and engines.”

Section 202(m)(5) of the CAA states that the Administrator shall require manufacturers to, “provide promptly to any person engaged in the repairing or servicing of motor vehicles or motor vehicle engines * * * with any and all information needed to make use of the emission control diagnostics system prescribed under this subsection and such other information including instructions for making emission related diagnosis and repairs.”

D. How Has EPA Chosen the Level of the Proposed Emissions Thresholds?

The OBD emissions thresholds that we are proposing are summarized in Tables II.B-1, II.C-1, II.H-1 and II.H-2. These tables show the actual threshold levels and how they relate to current emissions standards. Here, we wish to summarize how we chose those proposed thresholds. First, it is important to note that OBD is more than emissions thresholds. In fact, most OBD monitors are not actually tied to an emissions threshold. Instead, they monitor the performance of a given component or system and evaluate that performance based on electrical information (e.g., voltage within proper range) or temperature information (e.g., temperature within range), etc. Such monitors often detect malfunctions well before emissions are seriously compromised. Nonetheless, emissions thresholds are a critical element to OBD requirements since some components and systems, most notably any aftertreatment devices, cannot be monitored in simple electrical or temperature related terms. Instead, their operating characteristics can be measured and correlated to an emissions impact. This way, when those operating characteristics are detected, an unacceptable emissions increase can be inferred and a malfunction can be noted to the driver.

Part of the challenge in establishing OBD requirements is determining the point—the OBD threshold—at which an unacceptable emissions increase has occurred that is detectable by the best available OBD technology. Two factors have gone into our determination of the emissions thresholds we are proposing: technological feasibility; and the costs and emissions reductions associated with repairs initiated as a result of malfunctions found by OBD systems. The first of these factors is discussed in more detail in section III where we present our case for the technological feasibility of the thresholds. In summary, we believe that the thresholds we are proposing are, while challenging, technologically feasible in the 2010 and later timeframe. We have carefully considered monitoring system capability, sensor capability, emissions measurement capability, test-to-test variability and, perhaps most importantly, the manufacturers' engineering and test cell resources and have arrived at thresholds we believe can be met on one engine family per manufacturer in the 2010 model year and on all engine families by the 2013 model year.

We believe that the proposed thresholds strike the proper balance between environmental protection, OBD and various sensor capabilities, and avoidance of repairs whose costs could be high compared to their emission control results. One must keep in mind that increasingly stringent OBD thresholds (i.e., OBD detection at lower emissions levels) may lead to more durable emission controls due to a manufacturer's desire to avoid the negative impression given their product upon an OBD detection. Such an outcome would result in lower fleetwide emissions while increasing costs to manufacturers. However, increasingly stringent OBD thresholds may also lead to more OBD detections and more OBD induced repairs and, perhaps, many OBD induced repairs for malfunctions having little impact on emissions. Such an outcome would result in lower fleetwide emissions while increasing costs to both manufacturers and truck owners.

E. World Wide Harmonized OBD (WWH-OBD)

Within the United Nations (UN), the World Forum for Harmonization of Vehicle Regulations (WP.29) administers the 1958 Geneva Agreement (1958 Agreement) to facilitate the adoption of uniform conditions of approval and reciprocal recognition of approval for motor vehicle equipment and parts. As a result, WP.29 has responsibility for vehicle regulations within Europe and, indirectly, many countries outside of Europe that have voluntarily adopted the WP.29 regulations. The United States was never a party to the 1958 Agreement, but EPA has monitored the WP.29 regulations developed under the 1958 Agreement and we have benefited from a reciprocal consultative relationship with our European counterparts. More recently, WP.29 took on the responsibility of administering the 1998 Global Agreement that established a process to permit all regions of the world to jointly develop global technical regulations without required mutual recognition of approvals or designated compliance and enforcement. The United States is a signatory of the 1998 Global Agreement (1998 Agreement), and EPA has responsibility for representing the U.S. with respect to environmental issues within WP.29 as they pertain to the 1998 Agreement.

During the one-hundred-and-twenty-sixth session of WP.29 of March 2002, the Executive Committee (AC.3) of the 1998 Global Agreement (1998 Agreement) adopted a Programme of Work, which includes the development of a Global Technical Regulation (GTR) concerning onboard diagnostic systems for heavy-duty vehicles and engines. An informal working group—the WWH-OBD working group—was established to develop the GTR. The working group was instructed that the OBD system should detect failures from the engine itself, as well as from the exhaust aftertreatment systems fitted downstream of the engine, and from the package of information exchanged between the engine electronic control unit(s) and the rest of vehicle and/or powertrain. The working group was also instructed to base the OBD requirements on the technologies expected to be industrially available at the time the GTR would be enforced, and to take into account both the expected state of electronics in the years 2005-2008 and the expected newest engine and aftertreatment technologies.

In November 2003, AC.3 further directed the working group to structure the GTR in such a manner as to enable its future extension to other functions of the vehicle. In so doing, AC.3 did not revise the scope of the task given to the working group (i.e., the scope remained emissions-related heavy-duty OBD). As a result, the GTR is structured such that OBD monitoring and communications could be extended to other systems such as vehicle safety systems. This has been achieved by dividing the GTR into a set of generic OBD requirements to be followed by specific OBD requirements concerning any future desired OBD systems. The generic OBD requirements contain definitions and other OBD regulatory elements that are meant to be applicable throughout the GTR and all of its modules, annexes, and appendices. This generic section is followed by the first specific OBD section—emission-related OBD—which contains definitions and OBD regulatory elements specific to emissions-related OBD.

EPA has been active in the WWH-OBD working group for more than three

years. Because that group has been developing a regulation at the same time that we have been developing the requirements in this proposal, our proposed OBD requirements are consistent, for the most part, with the current efforts of the WWH-OBD group.

The WWH-OBD working group submitted a draft GTR as a formal document in March of 2006. During the months immediately following, the WWH-OBD working group has made final revisions to the GTR and will submit it to WP.29 for consideration. If approved by WP.29 and adopted as a formal global technical regulation, we would intend to propose any revisions to our OBD regulations that might be necessary to make them consistent with WWH-OBD.

Note that, while the WWH-OBD GTR is consistent with many of the specific requirements we are proposing, it is not currently as comprehensive as our proposal (e.g., it does not contain the same level of detail with respect to certification requirements and enforcement provisions). For that reason, at this time, we do not believe that the GTR would fully replace what we are proposing today.

The latest version of the draft WWH-OBD GTR has been placed in the docket for this rule.

While it is not yet a final document, we are nonetheless interested in comments regarding the current version. More specifically, we are interested in comments regarding any possible inconsistencies between the requirements of the draft GTR and the requirements being proposed today. We believe that if such inconsistencies exist, they are minor. WWH-OBD provides a framework for nations to establish a heavy-duty OBD program. It has the potential to result in similar OBD systems, but the WWH-OBD GTR must fit into the context of any country's existing heavy-duty emissions regulations. For example, at this time, the draft GTR does not specify emissions threshold levels, implementation dates, or phase-in schedules. As such, our proposal today is much more detailed than the draft WWH-OBD GTR, but we believe there exist no major inconsistencies between the two regulations.

“Revised Proposal for New Draft Global Technical Regulation (gtr): Technical Requirements for On-Board Diagnostic Systems (OBD) for Road Vehicles;” ECE/TRANS/WP.29/GRPE/2006/8/Rev.1; March 27, 2006, Docket ID# EPA-HQ-OAR-2005-0047-0004.

F. Onboard Diagnostics for Diesel Engines Used in Nonroad Land-Based Equipment

We are also considering regulations—although we are not making any proposals today—that would require OBD systems on heavy-duty diesel engines used in nonroad land-based equipment. The pollution emitted by diesel nonroad engines contributes greatly to our nation's continuing air quality problems. Our recent Nonroad Tier 4 rulemaking was designed to address these serious air quality problems from land-based diesel engines. (69 FR 38958) Like with diesel highway emissions, these problems include premature mortality, aggravation of respiratory and cardiovascular disease, aggravation of existing asthma, acute respiratory symptoms, chronic bronchitis, and decreased lung function. And, as noted above, we believe that diesel exhaust is likely to be carcinogenic to humans by inhalation and that this cancer hazard exists for occupational and environmental levels of exposure.

In our preamble to the Nonroad Tier 4 final rule, we estimated that, absent the nonroad Tier 4 standards, by 2020, land based nonroad diesel engines would account for as much as 70 percent of the diesel mobile source PM inventory. As part of our nonroad Tier 4 program, new emission standards will begin to take effect in calendar year 2011 that are based on the use of high-efficiency catalytic exhaust emission control devices or comparably effective advanced technologies. As with our 2007HD highway program, a cap is also included on the allowable sulfur content in nonroad diesel fuel.

The diesel engines used in nonroad land-based equipment are, in certain horsepower ranges, often essentially the same as those used in heavy-duty highway trucks. In other horsepower ranges—e.g., very large nonroad machines with engines having more than 1,500 horsepower—the engine is quite different. Such differences can include the addition of cylinders and turbo chargers among other things. Notably, the new nonroad Tier 4 regulations will result in the introduction of advanced emissions control systems on nonroad land-based equipment; those advanced emissions control systems will be the same type of systems as those expected for highway diesel engines.

Therefore, having OBD systems and OBD regulations for nonroad diesel engines seems to be a natural progression from the proposed requirements for heavy-duty highway engines. Nonetheless, we believe that there are differences between nonroad equipment and highway applications, and differences between the nonroad market and the highway market such that proposing the same OBD requirements for nonroad as for highway may not be appropriate. Therefore, we are providing advance notice to the public with the goal of soliciting public comment regarding how we should proceed with respect to nonroad OBD. This section presents issues we have identified and solicits comment. We also welcome comment with respect to other issues we have not addressed here, such as service information availability.

1. What Is the Baseline Nonroad OBD System?

We know that highway diesel engines already use a sophisticated level of OBD system. For nonroad diesel engines in the 200 to 600 horsepower range—i.e., the typical range of highway engines—are the current OBD system identical to their highway counterparts? How would the proposed highway OBD requirements change this, if at all? Do diesel engines outside the range typical of highway engines use OBD?

2. What Is the Appropriate Level of OBD Monitoring for Nonroad Diesel Engines?

The proposed OBD requirements for highway engines are very comprehensive and would result in virtually every element of the emissions control system being monitored. Is this appropriate for nonroad diesel engines? And to what degree should such monitoring be required? The emissions thresholds proposed for highway engines will push OBD and sensor technology beyond where it is today because of their stringency. Is a similar level of stringency appropriate for nonroad engines? Should emissions thresholds analogous to those presented in Table II.B-1 of this preamble even be a part of any potential nonroad OBD requirements or should nonroad OBD rely more heavily on comprehensive component monitoring as discussed in section II.D.4 of this preamble? This latter question is particularly compelling given the incredibly broad range of operating characteristics for nonroad equipment. Similar to the issue of emissions thresholds, certain aspects of the proposed highway OBD requirements carry with them serious concerns given the range of use for heavy-duty highway trucks (line-haul trucks versus garbage trucks versus urban delivery trucks, etc.). As discussed in various places in section II of this preamble, this broad range of uses makes it difficult for manufacturers to design a single approach that would, for example, ensure frequent monitoring events on all possible applications. This difficulty could be even more pronounced in the nonroad industry given the greater number of possible applications.

We request comment regarding what any potential nonroad OBD monitoring requirements should look like. More specifically, we request comment regarding the inclusion of emissions thresholds versus relying solely on comprehensive component monitoring. From commenters in favor of emissions thresholds, we request details regarding the appropriate level of emissions thresholds including data and strong engineering analyses for/against the suggested level. We request comment regarding the comprehensiveness of monitoring (i.e., the entire emissions control system, aftertreatement devices only, feedback control systems only, etc.).

3. What Should the OBD Standardization Features Be?

Should nonroad OBD include a requirement for a dedicated, OBD-only malfunction indicator light? Should nonroad OBD require specific communication protocols for communication of onboard information to offboard devices and scan tools? What should those protocols be? What are the needs of the nonroad service industry with respect to standardization of onboard to offboard communications?

4. What Are the Prospects and/or Desires for International Harmonization of Nonroad OBD?

Nonroad equipment is perhaps the most international of all mobile source equipment. Land based nonroad equipment, while not as much so as marine equipment, tends to be designed, produced, marketed, and sold to a world market to a greater extent than is highway equipment. Given that, is there a sense within the nonroad industry that international harmonization is important? Imperative? Is the proper avenue for putting into place nonroad OBD regulations the WWH-OBD process discussed above? If so, is industry prepared to play a role in developing a nonroad OBD element to the WWH-OBD document? Are other government representatives prepared to do so?

II. What Are the Proposed OBD Requirements and When Would They Be Implemented?

The following subsections describe our proposed OBD monitoring requirements and the timelines for their implementation. The requirements are indicative of our goal for the program which is a set of OBD monitors that provide robust diagnosis of the emission control system. Our intention is to provide industry sufficient time and experience with satisfying the demands of the proposed OBD program. While their engines already incorporate OBD systems, those systems are generally less comprehensive and do not monitor the emission control system in the ways we are proposing. Additionally, the proposed OBD requirements represent a new set of technological requirements and a new set of certification requirements for the industry in addition to the 2007HD highway program and its challenging emission standards for PM and NO

and other pollutants. As a result, we believe the monitoring requirements and timelines outlined in this section appropriately weigh the need for OBD monitors on the emission control system and the need to gain experience with not only those monitors but also the newly or recently added emission control hardware.

We request comment on all aspects of the requirements laid out in this section and throughout this preamble. As discussed in Section IX, we are also interested in comments concerning state run HDOBD-based inspection and maintenance (I/M) programs, the level of interest in such programs, and comments concerning the suitability of today's proposed OBD requirements toward facilitating potential HDOBD I/M programs in the future.

A. General OBD System Requirements

1. The OBD System

We are proposing that the OBD system be designed to operate for the actual life of the engine in which it is installed. Further, the OBD system cannot be programmed or otherwise designed to deactivate based on age and/or mileage of the vehicle during the actual life of the engine. This requirement is not intended to alter existing law and enforcement practice regarding a manufacturer's liability for an engine beyond its regulatory useful life, except where an engine has been programmed or otherwise designed so that an OBD system deactivates based on age and/or mileage of the engine.

We are also proposing that computer coded engine operating parameters not be changeable without the use of specialized tools and procedures (e.g. soldered or potted computer components or sealed (or soldered) computer enclosures). Upon Administrator approval, certain product lines may be exempted from this requirement if those product lines can be shown to not need such protections. In making the approval decision, the Administrator will consider such things as the current availability of performance chips, performance capability of the engine, and sales volume.

2. Malfunction Indicator Light (MIL) and Diagnostic Trouble Codes (DTC)

Upon detecting a malfunction within the emission control system,

the OBD system must make some indication to the driver so that the driver can take action to get the problem repaired. The proposal would require that a dashboard malfunction indicator light (MIL) be illuminated to inform the driver that a problem exists that needs attention. Upon illumination of the MIL, the proposal would require that a diagnostic trouble code (DTC) be stored in the engine's computer that identifies the detected malfunction. This DTC would then be read by a service technician to assist in making the necessary repair.

What constitutes a “malfunction” for over 14,000 pound applications under today's proposal is covered in section II.B for diesel engines, section II.C for gasoline engines, and section II.D for all engines.

Because the MIL is meant to inform the driver of a detected malfunction, we are proposing that the MIL be located on the driver's side instrument panel and be of sufficient illumination and location to be readily visible under all lighting conditions. We are proposing that the MIL be amber (yellow) in color when illuminated because yellow is synonymous with the notion of a “cautionary warning”; the use of red for the MIL would be strictly prohibited because red signifies “danger” which is not the proper message for malfunctions detected according to today's proposal. Further, we are proposing that, when illuminated, the MIL display the International Standards Organization (ISO) engine symbol because this symbol has become accepted after 10 years of light-duty OBD as a communicator of engine and emissions system related problems. We are also proposing that there be only one MIL used to indicate all malfunctions detected by the OBD system on a single vehicle. We believe this is important to avoid confusion over multiple lights and, potentially, multiple interpretations of those lights. Nonetheless, we seek comment on this limitation to one dedicated MIL to communicate emissions-related malfunctions. We also seek comment on the requirement that the MIL be amber in color since some trucks may use liquid crystal display (LCD) panels to display dashboard information and some such panels are monochromic and unable to display color.

We are also interested in comments regarding the malfunction indicator light and the symbol displayed to

communicate that there is an engine and/or emission-related malfunction. As noted, we are proposing use of the ISO engine symbol as shown in Table II.A-1. The U.S. Department of Transportation has proposed use of an alternative ISO symbol to denote, specifically, an emission-related malfunction. (68 FR 55217) That symbol is also shown in Table II.A-1. While we are not proposing that this alternative symbol be used, comments are solicited regarding whether this alternative symbol provides a clearer message to the driver.

Generally, a manufacturer would be allowed sufficient time to be certain that a malfunction truly exists before illuminating the MIL. No one benefits if the MIL illuminates spuriously when a real malfunction does not exist. Thus, for most OBD monitoring strategies, manufacturers would not be required to illuminate the MIL until a malfunction clearly exists which will be considered to be the case when the same problem has occurred on two sequential driving cycles.

Generally, a “driving cycle” or “drive cycle” consists of engine startup and engine shutoff or consists of four hours of continuous engine operation.

EP24JA07.000

To keep this clear in the onboard computer, we are proposing that the OBD system make certain distinctions between the problems it has detected, and that the system maintain a strict logic for diagnostic trouble code (DTC) storage/erasure and for MIL illumination/extinguishment. Whenever the enable criteria for a given monitor are met, we would expect that monitor to run. For continuous monitors, this would be during essentially all engine operation.

For non-continuous monitors, it would be during only a subset of engine operation.

In general, we are proposing that monitors make a diagnostic decision just once per drive cycle that contains operation satisfying the enable criteria for the given monitor.

A “continuous” monitor—if used in the context of monitoring conditions for circuit continuity, lack of circuit continuity, circuit faults, and out-of-range values—means sampling at a rate no less than two samples per second. If a computer input component is sampled less frequently for engine control purposes, the signal of the component may instead be evaluated each time sampling occurs.

A “non-continuous” monitor being a monitor that runs only when a limited set of operating conditions occurs.

When a problem is first detected, we are proposing that a “pending” DTC be stored. If, during the subsequent drive cycle that contains operation satisfying the enable criteria for the given monitor, a problem in the components/system is not again detected, the OBD system would declare that a malfunction does not exist and would, therefore, erase the pending DTC. However, if, during the subsequent drive cycle that contains operation satisfying the enable criteria for the given monitor, a problem in the component/system is again detected, a malfunction has been confirmed and, hence, a “confirmed” or “MIL-on” DTC would be stored.

Section II.F presents the requirements for standardization of OBD information and communications. Upon storage of a MIL-on DTC and, depending on the communication protocol used—ISO 15765-4 or SAE J1939—the pending DTC would either remain stored or be erased, respectively. Today's proposal neither stipulates which communication protocol nor which pending DTC logic be used. We are proposing to allow the use of either of the existing protocols as is discussed in more detail in section II.F. Upon storage of the MIL-on DTC, the MIL must be illuminated.

Also at this time, a “permanent” DTC would be stored (see section II.F.4 for more details regarding permanent DTCs and our rationale for proposing them).

Different industry standards organizations—the Society of Automotive Engineers (SAE) and the International Standards Organization (ISO)—use different terminology to refer to a “MIL-on” DTC. For clarity, we use the term “MIL-on” DTC throughout this preamble to convey the concept and not any requirement that standard making bodies use the term in their standards.

Throughout this proposal, we refer to MIL illumination to mean a steady, continuous illumination during engine operation unless stated otherwise. This contrasts with the MIL illumination logic used by many engine manufacturers today by which the MIL would illuminate upon detection of a malfunction but would remain illuminated only while the malfunction was actually occurring. Under this latter logic, an intermittent malfunction or one that occurs under only limited operating conditions may result in a MIL that illuminates, extinguishes, illuminates, etc., as operating conditions change.

A permanent DTC must be stored in a manner such that electrical disconnections do not result in their erasure (i.e., they must be stored in non-volatile random access memory (NVRAM)).

We are also proposing that, after three subsequent drive cycles that contain operation satisfying the enable criteria for the given monitor without any recurrence of the previously detected malfunction, the MIL should be extinguished (unless there are other MIL-on DTCs stored for which the MIL must also be illuminated), the permanent DTC should be erased, but a “previous-MIL-on” DTC should remain stored.

We are proposing that the previous MIL-on DTC remain stored for 40 engine warmup cycles after which time, provided the identified malfunction has not been detected again and the MIL is presently not illuminated for that malfunction, the previous-MIL-on DTC can be erased.

However, if an illuminated MIL is not extinguished, or if a MIL-on DTC is not erased, by the OBD system itself but is instead erased via scan tool or battery disconnect (which would erase all non-permanent, volatile memory), the permanent DTC must remain stored. This way, permanent DTCs can only be erased by the OBD system itself and cannot be erased through human interaction with the system.

This general “three trip” condition for extinguishing the MIL is true for all but two diesel systems/monitors—the misfire monitor and the SCR system—and three gasoline systems/monitors—the fuel system, the misfire monitor, and the evaporative system—which have further conditions on extinguishing the MIL This is discussed in more detail in sections II.B and II.C.

For simplicity, the discussion here refers to “previous-MIL-on” DTCs only. The ISO 15765 standard and the SAE J1939 standard use different terms to refer to the concept of a previous-MIL-on DTC. Our intent is to present the concept of our proposal in this preamble and not to specify the terminology used by these standard making bodies.

We are proposing that the manufacturer be allowed, upon

Administrator approval, to use alternative statistical MIL illumination and DTC storage protocols to those described above (i.e., alternatives to the “first trip—pending DTC, second strip—MIL-on DTC logic). The Administrator would consider whether the manufacturer provided data and/or engineering evaluation adequately demonstrates that the alternative protocols can evaluate system performance and detect malfunctions in a manner that is equally effective and timely. Alternative strategies requiring, on average, more than six driving cycles for MIL illumination would probably not be accepted.

Upon storage of either a pending DTC and/or a MIL-on DTC, we are proposing that the computer store a set of “freeze frame” data. This freeze frame data would provide a snap shot of engine operating conditions present at the time the malfunction occurred and was detected. This information serves the repair technician in diagnosing the problem and conducting the proper repair. The freeze frame data should be stored upon storage of a pending DTC. If the pending DTC matures to a MIL-on DTC, the manufacturer can choose to update the freeze frame data or retain the freeze frame stored in conjunction with the pending DTC. Likewise, any freeze frame stored in conjunction with any pending or MIL-on DTC should be erased upon erasure of the DTC. Further information concerning the freeze frame requirement and the data required in the freeze frame is presented in section II.F.4, below.

We are also proposing that the OBD system illuminate the MIL and store a MIL-on DTC to inform the vehicle operator whenever the engine enters a mode of operation that can affect the performance of the OBD system. If such a mode of operation is recoverable (i.e., operation automatically returns to normal at the beginning of the following ignition cycle

), then in lieu of illuminating the MIL when the mode of operation is entered, the OBD system may wait to illuminate the MIL and store the MIL-on DTC if the mode of operation is again entered before the end of the next ignition cycle. We are proposing this because many operating strategies are designed such that they continue automatically through to the next key-off. Regardless, upon the next key-on, the engine control would start off in “normal” operating mode and would return to the “abnormal” operating mode only if the condition causing the abnormal mode was again encountered. In such cases, we are proposing to allow that the MIL be illuminated during the second consecutive drive cycle during which such an “abnormal” mode is engaged.

“Ignition Cycle” means a drive cycle that begins with engine start and includes an engine speed that exceeds 50 to 150 rotations per minute (rpm) below the normal, warmed-up idle speed (as determined in the drive position for vehicles equipped with an automatic transmission) for at least two seconds plus or minus one second.

Note that we use the term “abnormal” to refer to an operating mode that the engine is designed to enter upon determining that “normal” operation cannot be maintained. Therefore, the term “abnormal” is somewhat of a misnomer since the engine is doing what it has been designed to do. Nonetheless, the abnormal operating mode is clearly not the operating mode the manufacturer has intended for optimal operation. Such operating modes are sometimes referred to as “default” operating modes or “limp-home” operating modes.

Whether or not the “abnormal” mode of operation is recoverable, in this context, has nothing to do with whether the detected malfunction goes away or stays. Instead, it depends solely on whether or not the engine, by design, will stay in abnormal operating mode on the next key-on. We are proposing this MIL logic because often the diagnostic (i.e., monitor) that caused the engine to enter abnormal mode cannot run again once the engine is in the abnormal mode. So, if the MIL logic associated with abnormal mode activation was always a two-trip diagnostic, abnormal mode activation would set a pending DTC on the first trip and, since the system would then be stuck in that abnormal operating mode and would never be able to run the diagnostic again, the pending DTC could never mature to a MIL-on DTC nor illuminate the MIL. Hence, the MIL must illuminate upon the first entry into such an abnormal operating mode. If such a mode is recoverable, the engine will start at the next key-on in “normal” mode allowing the monitor to run again and, assuming another detection of the condition, the system would set a MIL-on DTC and illuminate the MIL.

The OBD system would not need to store a DTC nor illuminate the MIL upon abnormal mode operation if other telltale conditions would result in immediate action by the driver. Such telltale conditions would be, for example, an overt indication like a red engine shut-down warning light. The OBD system also need not store a DTC nor illuminate the MIL upon abnormal mode operation if the mode is indeed an auxiliary emission control device (AECD) approved by the Administrator.

There may be malfunctions of the MIL itself that would prevent it from illuminating. A repair technician—or possibly an I/M inspector—would still be able to determine the status of the MIL (i.e., commanded “on” or “off”) by reading electronic information available through a scan tool, but there would be no indication to the driver of an emissions-related malfunction should one occur. Unidentified malfunctions may cause excess emissions to be emitted from the vehicle and may even cause subsequent deterioration or failure of other components or systems without the driver's knowledge. In order to prevent this, the manufacturer must ensure that the MIL is functioning properly. For this reason, we are proposing two requirements to check the functionality of the MIL itself. First, the MIL would be required to illuminate for a minimum of five seconds when the vehicle is in the key-on, engine-off position. This allows an interested party to check the MIL's functionality simply by turning the key to the key-on position. While the MIL would be physically illuminated during this functional check, the data stream value for the MIL command status would be required to indicate “off” during this check unless, of course, the MIL was currently being commanded “on” for a detected malfunction. This functional check of the MIL would not be required during vehicle operation in the key-on, engine-off position subsequent to the initial engine cranking of an ignition cycle (e.g., due to an engine stall or other non-commanded engine shutoff).

The second functional check requirement we are proposing requires the OBD system to perform a circuit continuity check of the electrical circuit that is used to illuminate the MIL to verify that the circuit is not shorted or open (e.g., a burned out bulb). While there would not be an ability to illuminate the MIL when such a malfunction is detected, the electronically readable MIL command status in the onboard computer would be changed from commanded “off” to “on”. This would allow the truck owner or fleet maintenance staff to quickly determine whether an extinguished MIL means “no malfunctions” or “broken MIL.” It would also serve, should it become of interest in the future, complete automation of the I/M process by eliminating the need for inspectors to input manually the results of their visual inspections. Feedback from passenger car I/M programs indicates that the current visual bulb check performed by inspectors is subject to error and results in numerous vehicles being falsely failed or passed. By requiring monitoring of the circuit itself, the entire pass/fail criteria of an I/M program could be determined by the electronic information available through a scan tool, thus better facilitating quick

and effective inspections and minimizing the chance for manually-entered errors.

At the manufacturer's option, the MIL may be used to indicate readiness status in a standardized format (see Section II.F) in the key-on, engine-off position. Readiness status is a term used in light-duty OBD that refers to a vehicle's readiness for I/M inspection. For a subset of monitors—those that are non-continuous monitors for which an emissions threshold exists (see sections II.B and II.C for more on emissions thresholds)—a readiness status indicator must be stored in memory to indicate whether or not that particular monitor has run enough times to make a diagnostic decision. Until the monitor has run sufficient times, the readiness status would indicate “not ready”. Upon running sufficient times, the readiness status would indicate “ready.” This serves to protect against drivers disconnecting their battery just prior to the I/M inspection so as to erase any MIL-on DTCs. Such an action would simultaneously set all readiness status indicators to “not ready” resulting in a notice to return to the inspection site at a future date. Readiness indicators also help repair technicians because, after completing a repair, they can operate the vehicle until the readiness status indicates “ready” and, provided no DTCs are stored, know that the repair has been successful. We are proposing that HDOBD systems follow this same readiness status logic as used for years in light-duty OBD both to assist repair technicians and to facilitate potential future HDOBD I/M programs.

We are also proposing that the manufacturer, upon Administrator approval, be allowed to use the MIL to indicate which, if any, DTCs are currently stored (e.g., to “blink” the stored codes). The Administrator would approve the request if the manufacturer can demonstrate that the method used to indicate the DTCs will not be unintentionally activated during any inspection test or during routine driver operation.

3. Monitoring Conditions

a. Background

Given that the intent of the proposed OBD requirements is to monitor the emission control system for proper operation, it is logical that the OBD monitors be designed such that they monitor the emission control system during typical driving conditions. While many OBD monitors would be designed such that they are continuously making decisions about the operational status of the engine, many—and arguably the most critical—monitors are not so designed. For example, an OBD monitor whose function is to monitor the active fuel injection system of a NO

adsorber or a DPF cannot be continuously monitoring that function since that function occurs on an infrequent basis. This OBD monitor presumably would be expected to “run,” or evaluate the active injection system, during an actual fuel injection event.

For this reason, manufacturers are allowed to determine the most appropriate times to run their non-continuous OBD monitors. This way, they are able to make an OBD evaluation either at the operating condition when an emission control system is active and its operational status can best be evaluated, and/or at the operating condition when the most accurate evaluation can be made (e.g., highly transient conditions or extreme conditions can make evaluation difficult). Importantly, manufacturers are prohibited from using a monitoring strategy that is so restrictive such that it rarely or never runs. To help protect against monitors that rarely run, we are proposing an “in-use monitor performance ratio” requirement which is detailed in section II.E.

The set of operating conditions that must be met so that an OBD monitor can run are called the “enable criteria” for that given monitor. These enable criteria are often different for different monitors and may well be different for different types of engines. A large diesel engine intended for use in a Class 8 truck would be expected to see long periods of relatively steady-state operation while a smaller engine intended for use in an urban delivery truck would be expected to see a lot of transient operation. Manufacturers will need to balance between a rather loose set of enable criteria for their engines and vehicles given the very broad range of operation HD highway engines see and a tight set of enable criteria given the desire for greater monitor accuracy.

b. General Monitoring Conditions

i. Monitoring Conditions for All Engines

As guidance to manufacturers, we are proposing the following criteria to assist manufacturers in developing their OBD enable criteria. These criteria would be used by the Agency during our OBD certification approval process to ensure that monitors run on a frequent basis during real world driving conditions. These criteria would be:

• The monitors should run during conditions that are technically necessary to ensure robust detection of malfunctions (e.g., to avoid false passes and false indications of malfunctions);

• The monitor enable criteria should ensure monitoring will occur during normal vehicle operation; and,

• Monitoring should occur during at least one test used by EPA for emissions verification “ either the HD Federal Test Procedure (FTP) transient cycle, or the Supplementary Emissions Test (SET).

See 40 CFR part 86, subpart N for details of EPA's test procedures.

As discussed in more detail in sections II.B through II.D, we are proposing that manufacturers define the monitoring conditions, subject to Administrator approval, for detecting the malfunctions required by this proposal. The Administrator would determine if the monitoring conditions proposed by the manufacturer for each monitor abide by the above criteria.

In general, except as noted in sections II.B through II.D, the proposed regulation would require each monitor to run at least once per driving cycle in which the applicable monitoring conditions are met. The proposal would also require certain monitors to run continuously throughout the driving cycle. These include a few threshold monitors (e.g., fuel system monitor) and most circuit continuity monitors. While a basic definition of a driving cycle (e.g., from ignition key-on and engine startup to engine shutoff) has been sufficient for passenger cars, the driving habits of many types of vehicles in the heavy-duty industry dictate an alternate definition. Specifically, many heavy-duty operators will start the engine and leave it running for an entire day or, in some cases, even longer. As such, we are proposing that any period of continuous engine-on operation of four hours be considered a complete driving cycle. A new driving cycle would begin following such a four hour period, regardless of whether or not the engine had been shut down. Thus, the “clock” for monitors that are required to run once per driving cycle would be reset to run again (in the same key-on engine start or trip) once the engine has been operated beyond four hours continuously. This would avoid an unnecessary delay in detection of malfunctions simply because the heavy-duty vehicle operator has elected to leave the vehicle running continuously for an entire day or days at a time.

Manufacturers may request Administrator approval to define monitoring conditions that are not encountered during the FTP cycle. In evaluating the manufacturer's request, the Administrator will consider the degree to which the requirement to run

during the FTP cycle restricts in-use monitoring, the technical necessity for defining monitoring conditions that are not encountered during the FTP cycle, data and/or an engineering evaluation submitted by the manufacturer which demonstrate that the component/system does not normally function, or monitoring is otherwise not feasible, during the FTP cycle, and, where applicable, the ability of the manufacturer to demonstrate that the monitoring conditions will satisfy the minimum acceptable in-use monitor performance ratio requirement as defined below.

ii. In-Use Performance Tracking Monitoring Conditions

In addition to the general monitoring conditions above, we are proposing that manufacturers be required to implement software algorithms in the OBD system to individually track and report in-use performance of the following monitors in the standardized format specified in section II.E:

• Diesel NMHC converting catalyst(s)

• Diesel NO

converting catalyst(s)

• Gasoline catalyst(s)

• Exhaust gas sensor(s)

• Gasoline evaporative system

• Exhaust gas recirculation (EGR) system

• Variable valve timing (VVT) system

• Gasoline secondary air system

• Diesel particulate filter system

• Diesel boost pressure control system

• Diesel NO

adsorber(s)

The OBD system is not required to track and report in-use performance for monitors other than those specifically identified above.

iii. In-Use Performance Ratio Requirement

We are also proposing that, for all 2013 and subsequent model year engines, manufacturers be required to define monitoring conditions that, in addition to meeting the general monitoring conditions, ensure that certain monitors yield an in-use performance ratio (which monitors and the details that define the performance ratio are defined in section II.E) that meets or exceeds the minimum acceptable in-use monitor performance ratio for in-use vehicles. We are proposing a minimum acceptable in-use monitor performance ratio of 0.100 for all monitors specifically required to track in-use performance. This means that the monitors listed in section II.A.3.ii above must run and make valid diagnostic decisions during 10 percent of the vehicle's trips. We intend to work with industry during the initial years of implementation to gather data on in-use performance ratios and may revise this ratio lower as appropriate depending on what we learn.

Note that manufacturers may not use the calculated ratio (or any element thereof), or any other indication of monitor frequency, as a monitoring condition for a monitor. For example, the manufacturer would not be allowed to use a low ratio to enable more frequent monitoring through diagnostic executive priority or modification of other monitoring conditions, or to use a high ratio to enable less frequent monitoring.

4. Determining the Proper OBD Malfunction Criteria

For determining the malfunction criteria for diesel engine monitors associated with an emissions threshold (see sections II.B and II.C for more on emissions thresholds), we are proposing that manufacturers be required to determine the appropriate emissions test cycle such that the most stringent monitor would result. In general, we believe that manufacturers can make this determination based on engineering judgement, but there may be situations where testing would be required to make the determination. We do not necessarily anticipate challenging a manufacturer's determination of which test cycle to use. Nonetheless, the manufacturer should be prepared, perhaps with test data, to justify their determination.

We are also proposing that, for engines equipped with emission controls that experience infrequent regeneration events (e.g., a DPF and/or a NO

adsorber), a manufacturer must adjust the emission test results for monitors that are required to indicate a malfunction before emissions exceed a certain emission threshold.

For each such monitor, the manufacturer would have to adjust the emission result as done in accordance with the provisions of section 86.004-28(i) with the component for which the malfunction criteria are being established having been deteriorated to the malfunction threshold. As proposed, the adjusted emission value must be used for purposes of determining whether or not the applicable emission threshold is exceeded.

See proposed § 86.010-18(f).

While we believe that this adjustment process for monitors of systems that experience infrequent regeneration events makes sense and would result in robust monitors, we also believe that it could prove to be overly burdensome for manufacturers. For example, a NO

adsorber threshold being evaluated by running an FTP using a “threshold” part (i.e., a NO

adsorber deteriorated such that tailpipe emissions are at the applicable thresholds) may be considered acceptable provided the NO

adsorber does not regenerate during the test, but it may be considered unacceptable if the NO

adsorber does happen to regenerate during the test. This could happen because emissions would be expected to increase slightly during the regeneration event thereby causing emissions to be slightly above the applicable threshold. This would require the manufacturer to recalibrate the NO

adsorber monitor to detect at a lower level of deterioration to ensure that a regeneration event would not cause an exceedance of the threshold during an emissions test. After such a recalibration, the emissions occurring during the regeneration event would be lower than before because the new “threshold” NO

adsorber would have a slightly higher conversion efficiency. We are concerned that manufacturers may find themselves in a difficult iterative process calibrating such monitors that, in the end, will not be correspondingly more effective.

For this reason, we request comment regarding the burden associated with the need to consider regeneration events in determining compliance with emissions thresholds. We also request comment on how to address any environmental concern versus the burden. Would it perhaps be best to simply use the emissions adjustments that are determined in accordance with section 86.004-28(i)? Is it necessary to even consider regeneration emissions when determining emission threshold compliance or is it perhaps best to ignore regeneration events in determining threshold calibrations?

B. Monitoring Requirements and Timelines for Diesel-Fueled/Compression-Ignition Engines

Table II.B-1 summarizes the proposed diesel fueled compression ignition emissions thresholds at which point a component or system has failed to the point of requiring an illuminated MIL and a stored DTC. More detail regarding the specific monitoring requirements, implementation schedules, and liabilities can be found in the sections that follow.

Table II.B-1.—Proposed Emissions Thresholds for Diesel Fueled CI Engines over 14,000 Pounds

Component/monitor

NMHC

NMHC catalyst system

2010-2012

2.5x

2013+

catalyst system

2010+

+0.3

DPF system

2010-2012

2.5x

0.05/+0.04

2013+

0.05/+0.04

Air-fuel ratio sensors upstream

2010-2012

2.5x

+0.3

0.03/+0.02

2013+

+0.3

0.03/+0.02

Air-fuel ratio sensors downstream

2010-2012

2.5x

+0.3

0.05/+0.04

2013+

+0.3

0.05/+0.04

sensors

2010+

+0.3

0.05/+0.04

“Other monitors” with emissions thresholds (see section II.B)

2010-2012

2.5x

+0.3

0.03/+0.02

2013+

+0.3

0.03/+0.02

Notes:

MY=Model Year; 2.5x means a multiple of 2.5 times the applicable emissions standard or family emissions limit (FEL); +0.3 means the standard or FEL plus 0.3; 0.05/+0.04 means an absolute level of 0.05 or an additive level of the standard or FEL plus 0.04, whichever level is higher; not all proposed monitors have emissions thresholds but instead rely on functionality and rationality checks as described in section II.D.4.

There are exceptions to the emissions thresholds shown in Table II.B-1 whereby a manufacturer can demonstrate that emissions do not exceed the threshold even when the component or system is non-functional at which point a functional check would be allowed.

Note that, in general, the monitoring strategies designed to meet the requirements discussed below should not involve the alteration of the engine control system or the emissions control system such that tailpipe emissions would increase. We do not want emissions to increase, even for short durations, for the sole purpose of monitoring the systems intended to control emissions. The Administrator would consider such monitoring strategies on a case-by-case basis taking into consideration the emissions impact and duration of the monitoring event. However, much effort has been expended in recent years to minimize engine operation that results in increased emissions and we encourage manufacturers to develop monitoring strategies that do not require alteration of the basic control system.

1. Fuel System Monitoring

a. Background

The fuel system of a diesel engine is an essential component of the engine's emissions control system. Proper delivery of fuel—quantity, pressure, and timing—can play a crucial role in maintaining low engine-out emissions. The performance of the fuel system is also critical for aftertreatment device control strategies. As such, thorough monitoring of the fuel system is an essential element in an OBD system. The fuel system is primarily comprised of a fuel pump, fuel pressure control device, and fuel injectors. Additionally, the fuel system generally has sophisticated control strategies that utilize one or more feedback sensors to ensure the proper amount of fuel is being delivered to the cylinders. While gasoline engines have undergone relatively minor hardware changes (but substantial fine-tuning in the control strategy and feedback inputs), diesel engines have more recently undergone substantial changes to the fuel system hardware and now incorporate more refined control strategies and feedback inputs.

For diesel engines, a substantial change has occurred in recent years as manufacturers have transitioned to new high-pressure fuel systems. One of the most widely used is a high-pressure common-rail fuel injection system, which is generally comprised of a high-pressure fuel pump, a fuel rail pressure sensor, a common fuel rail that feeds all injectors, individual fuel injectors that directly control fuel injection quantity and timing for each cylinder, and a closed-loop feedback system that uses the fuel rail pressure sensor to achieve the commanded fuel rail pressure. Unlike older style fuel systems where fuel pressure was mechanically linked to engine speed (and thus, varied from low to high as engine speed increased), common-rail systems are capable of controlling fuel pressure independent of engine speed. This increase in fuel pressure control allows greater flexibility in optimizing the performance and emission characteristics of the engine. The ability of the system to generate high pressure independent of engine speed also improves fuel delivery at low engine speeds.

Precise control of the fuel injection timing is crucial for optimal engine and emission performance. As injection timing is advanced (i.e., fuel injection occurs earlier), hydrocarbon (HC) emissions and fuel consumption are decreased but oxides of nitrogen (NO

) emissions are increased. As injection timing is retarded (i.e., fuel injection occurs later), NO

emissions can be reduced but HC emissions, particulate matter (PM) emissions, and fuel consumption increase. Most modern diesel fuel systems even provide engine manufacturers with the ability to separate a single fuel injection event into discrete events such as pilot (or pre) injection, main injection, and post injection.

Given the important role that modern diesel fuel systems play in emissions control, malfunctions or deterioration that would affect the fuel pressure control, injection timing, pilot/main/post injection timing or quantity, or ability to accurately perform rate-shaping could lead to substantial increases in emissions (primarily NO

or PM), often times with an associated change in fuel consumption.

b. Fuel System Monitoring Requirements

We are proposing that the OBD system monitor the fuel delivery system to verify that it is functioning properly. The fuel system monitor would be required to monitor for malfunctions in the injection pressure control, injection quantity, injection timing, and feedback control (if equipped). The individual electronic components (e.g., actuators, valves, sensors, pumps) that are used in the fuel system and not specifically addressed in this section shall be monitored in accordance with the comprehensive component requirements in section II.D.4.

i. Fuel System Pressure Control

We are proposing that the OBD system continuously monitor the fuel system's ability to control to the desired fuel pressure. The OBD system would have to detect a malfunction of the fuel system's pressure control system when

the pressure control system is unable to maintain an engine's emissions at or below the emissions thresholds for “other monitors” as shown in Table II.B-1. For engines in which no failure or deterioration of the fuel system pressure control could result in an engine's emissions exceeding the applicable emissions thresholds, the OBD system would be required to detect a malfunction when the system has reached its control limits such that the commanded fuel system pressure cannot be delivered.

ii. Fuel System Injection Quantity

We are proposing that the OBD system detect a malfunction of the fuel injection system when the system is unable to deliver the commanded quantity of fuel necessary to maintain an engine's emissions at or below the emissions thresholds for “other monitors” as shown in Table II.B-1. For engines in which no failure or deterioration of the fuel injection quantity could result in an engine's emissions exceeding the applicable emissions thresholds, the OBD system would be required to detect a malfunction when the system has reached its control limits such that the commanded fuel quantity cannot be delivered.

iii. Fuel System Injection Timing

We are proposing that the OBD system detect a malfunction of the fuel injection system when the system is unable to deliver fuel at the proper crank angle/timing (e.g., injection timing too advanced or too retarded) necessary to maintain an engine's emissions at or below the emissions thresholds for “other monitors” as shown in Table II.B-1. For engines in which no failure or deterioration of the fuel injection timing could result in an engine's emissions exceeding the applicable emissions thresholds, the OBD system would be required to detect a malfunction when the system has reached its control limits such that the commanded fuel injection timing cannot be achieved.

iv. Fuel System Feedback Control

If the engine is equipped with feedback control of the fuel system (e.g., feedback control of pressure or pilot injection quantity), we are proposing that the OBD system detect a malfunction when and if:

• The system fails to begin feedback control within a manufacturer specified time interval;

• A failure or deterioration causes open loop or default operation; or

• Feedback control has used up all of the adjustment allowed by the manufacturer.

A manufacturer may temporarily disable monitoring for malfunctions where the feedback control has used up all of the adjustment allowed by the manufacturer during conditions that the monitor cannot distinguish robustly between a malfunctioning system and a properly operating system. To do so, the manufacturer would be required to submit data and/or engineering analyses demonstrating that the control system, when operating as designed on an engine with all emission controls working properly, routinely operates during these conditions with all of the adjustment allowed by the manufacturer used up. In lieu of detecting, with a fuel system specific monitor, when the system fails to begin feedback control within a manufacturer specified time interval and/or when a failure or deterioration causes open loop or default operation, the OBD system may monitor the individual parameters or components that are used as inputs for fuel system feedback control provided that the monitors detect all malfunctions related to feedback control.

c. Fuel System Monitoring Conditions

The OBD system would be required to monitor continuously for malfunctions of the fuel pressure control and feedback control. Manufacturers would be required to define the monitoring conditions for malfunctions of the injection quantity and injection timing such that the minimum performance ratio requirements discussed in section II.E would be met.

d. Fuel System MIL Illumination and DTC Storage

We are proposing the general MIL illumination and DTC storage requirements as discussed in section II.A.2.

2. Engine Misfire Monitoring

a. Background

Misfire, the lack of combustion in the cylinder, causes increased engine-out hydrocarbon emissions. On gasoline engines, misfire results from the absence of spark, poor fuel metering, and poor compression. Further, misfire can be intermittent on gasoline engines (e.g., the misfire only occurs under certain engine speeds or loads). Consequently, our existing under 14,000 pound OBD regulation requires continuous monitoring for misfire malfunctions on gasoline engines.

In contrast, manufacturers have historically maintained that a diesel engine with traditional diesel technology misfires only due to poor compression (e.g., worn valves or piston rings, improper injector or glow plug seating). They have also maintained that, when poor compression results in a misfiring cylinder, the cylinder will misfire under all operating conditions rather than only some operating conditions. For that reason, our existing under 14,000 pound OBD regulation has not required continuous monitoring for misfire malfunctions on diesel engines.

However, with the increased use of EGR and its use to varying degrees at different speeds and load, and with emerging technologies such as homogeneous charge compression ignition (HCCI), we believe that the conventional wisdom regarding diesel engines and misfires no longer holds true. These newer technologies may indeed result in misfires that are intermittent, spread out among various cylinders, and that only happen at certain speeds and loads.

b. Misfire Monitoring Requirements

We are proposing that the OBD system monitor the engine for misfire causing excess emissions. The OBD system must be capable of detecting misfire occurring in one or more cylinders. To the extent possible without adding hardware for this specific purpose, the OBD system must also identify the specific misfiring cylinder. If more than one cylinder is continuously misfiring, a separate DTC must be stored indicating that multiple cylinders are misfiring. When identifying multiple cylinder misfire, the OBD system is not required to also identify each of the continuously misfiring cylinders individually through separate DTCs.

For 2013 and subsequent model year engines, we are proposing a more stringent requirement that the OBD system detect a misfire malfunction causing emissions to exceed the emissions thresholds for “other monitors” as shown in Table II.B-1. This requirement to detect engine misfire prior to exceeding an emissions threshold would apply only to those engines equipped with sensors capable of detecting combustion or combustion quality (e.g., cylinder pressure sensors used in homogeneous charge compression ignition (HCCI) control systems). Engines without such sensors would have to detect only when one or more cylinders are continually misfiring.

To determine what level of misfire would cause emissions to exceed the applicable emissions thresholds, we are proposing that manufacturers determine

the percentage of misfire evaluated in 1000 revolution increments that would cause emissions from an emission durability demonstration engine to exceed the emissions thresholds if the percentage of misfire were present from the beginning of the test. To establish this percentage of misfire, the manufacturer would utilize misfire events occurring at equally spaced, complete engine cycle intervals, across randomly selected cylinders throughout each 1000-revolution increment. If this percentage of misfire is determined to be lower than one percent, the manufacturer may set the malfunction criteria at one percent. Any malfunction should be detected if the percentage of misfire established via this testing is exceeded regardless of the pattern of misfire events (e.g., random, equally spaced, continuous).

The manufacturer may employ other revolution increments besides the 1000 revolution increment being proposed. To do so, the manufacturer would need to demonstrate that the strategy would be equally effective and timely in detecting misfire.

c. Engine Misfire Monitoring Conditions

For engines without combustion sensors, we are proposing that the OBD system monitor for misfire during engine idle conditions at least once per drive cycle in which the monitoring conditions for misfire are met. The manufacturer would be required to define monitoring conditions, supported by manufacturer-submitted data and/or engineering analyses, that demonstrate that the monitoring conditions: are technically necessary to ensure robust detection of malfunctions (e.g., avoid false passes and false detection of malfunctions); require no more than 1000 cumulative engine revolutions; and, do not require any single continuous idle operation of more than 15 seconds to make a determination that a malfunction is present (e.g., a decision can be made with data gathered during several idle operations of 15 seconds or less).

For 2013 and subsequent model year engines with combustion sensors, we are proposing that the OBD system continuously monitor for misfire under all positive torque engine speeds and load conditions. If a monitoring system cannot detect all misfire patterns under all positive torque engine speeds and load conditions, the manufacturer may request that the Administrator approve the monitoring system nonetheless. In evaluating the manufacturer's request, the Administrator would consider the following factors: the magnitude of the region(s) in which misfire detection is limited; the degree to which misfire detection is limited in the region(s) (i.e., the probability of detection of misfire events); the frequency with which said region(s) are expected to be encountered in-use; the type of misfire patterns for which misfire detection is troublesome; and demonstration that the monitoring technology employed is not inherently incapable of detecting misfire under required conditions (i.e., compliance can be achieved on other engines). The evaluation would be based on the following misfire patterns: equally spaced misfire occurring on randomly selected cylinders; single cylinder continuous misfire; and, paired cylinder (cylinders firing at the same crank angle) continuous misfire.

d. Engine Misfire MIL Illumination and DTC Storage

For engines without combustion sensors, we are proposing the general MIL illumination and DTC storage requirements as discussed in section II.A.2.

For 2013 and subsequent model year engines with combustion sensors, we are proposing that, after four detections of the percentage of misfire that would cause emissions to exceed the applicable emissions thresholds during a single driving cycle, a pending DTC would be stored. If a pending DTC is stored, the OBD system would be required to illuminate the MIL and store a MIL—on DTC if the percentage of misfire is again exceeded four times during either: the driving cycle immediately following the storage of the pending DTC, regardless of the conditions encountered during the driving cycle; or, the next driving cycle in which similar conditions are encountered to the engine conditions that occurred when the pending DTC was stored.

For erasure of the pending DTC, we are proposing if, by the end of the next driving cycle in which similar conditions have been encountered to the engine conditions that occurred when the pending DTC was stored without an exceedance of the specified percentage of misfire, the pending DTC may be erased. The pending DTC may also be erased if similar conditions are not encountered during the next 80 driving cycles immediately following initial detection of the malfunction.

“Similar conditions,” as used in conjunction with misfire and fuel system monitoring, means engine conditions having an engine speed within 375 rpm, load conditions within 20 percent, and the same warm up status (i.e., cold or hot) as existing during the applicable previous problem detection. The Administrator may approve other definitions of similar conditions based on comparable timeliness and reliability in detecting similar engine operation.

We are proposing some specific items with respect to freeze frame storage associated with engine misfire. The OBD system shall store and erase freeze frame conditions either in conjunction with storing and erasing a pending DTC or in conjunction with storing a MIL—on DTC and erasing a MIL—on DTC. In addition to those proposed requirements discussed in section II.A.2, we are proposing that, if freeze frame conditions are stored for a malfunction other than a misfire malfunction when a DTC is stored, the previously stored freeze frame information shall be replaced with freeze frame information regarding the misfire malfunction (i.e., the misfire's freeze frame information should take precedence over freeze frames for other malfunctions). Further, we are proposing that, upon detection of misfire, the OBD system store the following engine conditions: engine speed, load, and warm up status of the first misfire event that resulted in the storage of the pending DTC.

Lastly, we are proposing that the MIL may be extinguished after three sequential driving cycles in which similar conditions have been encountered without an exceedance of the specified percentage of misfire.

3. Exhaust Gas Recirculation (EGR) System Monitoring

a. Background

Exhaust gas recirculation (EGR) systems are currently being used by many heavy-duty engine manufacturers to meet the 2.5 g/bhp-hr NO

+NMHC standard for 2004 and later model year engines. (65 FR 59896) EGR reduces NO

emissions in several ways. First, the recirculated exhaust gases dilute the intake air—i.e., oxygen in the fresh air is displaced with relatively non-reactive exhaust gases—which, in turn, results in less oxygen to form NO

. Second, EGR absorbs heat from the combustion process which reduces combustion chamber temperatures which, in turn, reduces NO

formation. The amount of heat absorbed from the combustion process is a function of EGR flow rate and recirculated gas temperature, both of which are controlled to minimize NO

emissions. An EGR cooler can be added to the EGR system to lower the recirculated gas temperature which further enhances NO

control. We fully expect that 2007 and later model year engines will continue to make use of cooled EGR systems.

While in theory the EGR system simply routes some exhaust gas back to the intake, production systems can be complex and involve many components to ensure accurate control of EGR flow

to maintain acceptable PM and NO

emissions while minimizing effects on fuel economy. To control EGR flow rates, EGR systems normally use the following components: an EGR valve, valve position sensor, boost pressure sensor, intake temperature sensor, intake (fresh) airflow sensor, and tubing or piping to connect the various components of the system. EGR temperature sensors and exhaust backpressure sensors can also be used. Additionally, some systems use a variable geometry turbocharger to provide the backpressure necessary to drive the EGR flow. Therefore, EGR is not a stand alone emission control device. Rather, it is carefully integrated with the air handling system (turbocharging and intake cooling) to control NO

while not adversely affecting PM emissions and fuel economy.

b. EGR System Monitoring Requirements

We are proposing that the OBD system monitor the EGR system on engines so equipped for low EGR flow rate, high EGR flow rate, and slow EGR flow response malfunctions. For engines so equipped, we are proposing that the EGR feedback control be monitored. Also, for engines equipped with EGR coolers (e.g., heat exchangers), the OBD system would have to monitor the cooler for malfunctions associated with insufficient EGR cooling. The individual electronic components (e.g., actuators, valves, sensors) that are used in the EGR system would be monitored in accordance with the comprehensive component requirements presented in section II.D.4.

i. EGR Low Flow Malfunctions

We are proposing that the OBD system detect a malfunction prior to a decrease from the manufacturer's specified EGR flow rate that would cause an engine's emissions to exceed the emissions thresholds for “other monitors” as shown in Table II.B-1. For engines in which no failure or deterioration of the EGR system that causes a decrease in flow could result in an engine's emissions exceeding the applicable emissions thresholds, the OBD system would have to detect a malfunction when the system has reached its control limits such that it cannot increase EGR flow to achieve the commanded flow rate.

ii. EGR High Flow Malfunctions

We are proposing that the OBD system detect a malfunction of the EGR system, including a leaking EGR valve—i.e., exhaust gas flowing through the valve when the valve is commanded closed—prior to an increase from the manufacturer's specified EGR flow rate that would cause an engine's emissions to exceed the emissions thresholds for “other monitors” as shown in Table II.B-1. For engines in which no failure or deterioration of the EGR system that causes an increase in flow could result in an engine's emissions exceeding the applicable emissions thresholds, the OBD system would have to detect a malfunction when the system has reached its control limits such that it cannot reduce EGR flow to achieve the commanded flow rate.

iii. EGR Slow Response Malfunctions

We are proposing that the OBD system detect a malfunction of the EGR system prior to any failure or deterioration in the capability of the EGR system to achieve the commanded flow rate within a manufacturer-specified time that would cause an engine's emissions to exceed the emissions thresholds for “other monitors” as shown in Table II.B-1. The OBD system would have to monitor both the capability of the EGR system to respond to a commanded increase in flow and the capability of the EGR system to respond to a commanded decrease in flow.

iv. EGR Feedback Control

We are proposing that the OBD system on any engine equipped with feedback control of the EGR system (e.g., feedback control of flow, valve position, pressure differential across the valve via intake throttle or exhaust backpressure), detect a malfunction when and if:

• The system fails to begin feedback control within a manufacturer specified time interval;

• A failure or deterioration causes open loop or default operation; or

• Feedback control has used up all of the adjustment allowed by the manufacturer.

v. EGR Cooler Performance

We are proposing that the OBD system detect a malfunction of the EGR cooler prior to a reduction from the manufacturer's specified cooling performance that would cause an engine's emissions to exceed the emissions thresholds for “other monitors” as shown in Table II.B-1. For engines in which no failure or deterioration of the EGR cooler could result in an engine's emissions exceeding the applicable emissions thresholds, the OBD system would have to detect a malfunction when the system has no detectable amount of EGR cooling.

c. EGR System Monitoring Conditions

We are proposing that the OBD system monitor continuously for low EGR flow, high EGR flow, and feedback control malfunctions. Manufacturers would be required to define the monitoring conditions for EGR slow response malfunctions such that the minimum performance ratio requirements discussed in section II.E would be met with the exception that monitoring must occur every time the monitoring conditions are met during the driving cycle in lieu of once per driving cycle as required for most monitors. For purposes of tracking and reporting as required in section II.E, all monitors used to detect EGR slow response malfunctions must be tracked separately but reported as a single set of values as specified in section II.E.

For specific components or systems that have multiple monitors that are required to be reported (e.g., exhaust gas sensor bank 1 may have multiple monitors for sensor response or other sensor characteristics), the OBD system must separately track numerators and denominators for each of the specific monitors and report only the corresponding numerator and denominator for the specific monitor that has the lowest numerical ratio. If two or more specific monitors have identical ratios, the corresponding numerator and denominator for the specific monitor that has the highest denominator shall be reported for the specific component.

Manufacturersmay temporarily disable the EGR system check under specific conditions (e.g., when freezing may affect performance of the system). To do so, the manufacturer would be required to submit data and/or engineering analyses that demonstrate that a reliable check cannot be made when these specific conditions exist.

d. EGR System MIL Illumination and DTC Storage

We are proposing the general requirements for MIL illumination and DTC storage as discussed in section II.A.2.

4. Turbo Boost Control System Monitoring

a. Background

Turbochargers are used on internal combustion engines to enhance performance by increasing the density of the intake air. Some of the benefits of turbocharging include increased horsepower, improved fuel economy, and decreased exhaust smoke. Most modern diesel engines take advantage of these benefits and are equipped with turbocharging systems. Moreover, smaller turbocharged diesel engines can be used in place of larger non-turbocharged engines to achieve the desired engine performance characteristics.

Exhaust gases passing through the turbine cause it to spin which, in turn, causes an adjacent centrifugal pump on the same rotating shaft to spin. The spinning pump serves to compress the intake air thereby increasing its density. Typically, a boost pressure sensor is located in the intake manifold to provide a feedback signal of the current intake manifold pressure. As turbo speed (boost) increases, the pressure in the intake manifold also increases.

Proper boost control is essential to optimize emission levels. Even short periods of over-or under-boost can result in undesired air-fuel ratio excursions and corresponding emission increases. Additionally, the boost control system directly affects exhaust and intake manifold pressures. Another critical emission control system, EGR, is very dependent on these two pressures and generally uses the differential between them to force exhaust gas into the intake manifold. If the boost control system is not operating correctly, the exhaust or intake pressures may not be as expected and the EGR system may not function as designed. In high-pressure EGR systems, higher exhaust pressures will generate more EGR flow and, conversely, lower pressures will reduce EGR flow. A malfunction that causes excessive exhaust pressures (e.g., wastegate stuck closed at high engine speed) can produce higher EGR flowrates at high load conditions and have a negative impact on emissions.

Manufacturers commonly use charge air coolers to maximize the benefits of turbocharging and to control NO

emissions. As the turbocharger compresses the intake air, the temperature of that intake air increases. This increasing air temperature causes the air to expand, which conflicts with one of the goals of turbocharging which is to increase charge air density. Charge air coolers are used to exchange heat between the compressed air and ambient air (or coolant) and cool the compressed air. Accordingly, a decrease in charge air cooler performance can affect emissions by causing higher intake air temperatures that can lead to higher combustion temperatures and higher NO

emissions.

One drawback of turbocharging is known as turbo lag. Turbo lag occurs when the driver attempts to accelerate quickly from a low engine speed. Since the turbocharger is a mechanical device, a delay exists from the driver demand for more boost until the exhaust flow can physically speed up the turbocharger enough to deliver that boost. In addition to a negative effect on driveability and performance, improper fueling (e.g., over-fueling) during this lag can cause emission increases (typically PM).

To decrease the effects of turbo lag, manufacturers design turbos that spool up quickly at low engine speeds and low exhaust flowrates. However, designing a turbo that will accelerate quickly from a low engine speed but will not result in an over-speed/over-boost condition at higher engine speeds is challenging. That is, as the engine speed and exhaust flowrates near their maximum, the turbo speed increases to levels that cause excessive boost pressures and heat that could lead to engine or turbo damage. To prevent excessive turbine speeds and boost pressures at higher engine speeds, a wastegate is often used to bypass part of the exhaust stream around the turbocharger. The wastegate valve is typically closed at lower engine speeds so that all exhaust is directed through the turbocharger, thus providing quick response from the turbocharger when the driver accelerates quickly from low engine speeds. The wastegate is then opened at higher engine speeds to prevent engine or turbo damage from an over-speed condition.

An alternative to a wastegate is the variable geometry turborcharger (VGT). To prevent over-boost conditions and to decrease turbo lag, VGTs are designed such that the geometry of the turbocharger changes with engine speed. While various physical mechanisms are used to achieve the variable geometry, the overall result is essentially the same. At low engine speeds, the exhaust gas into the turbo is restricted in a manner that maximizes the use of the available energy to spin the turbo. This allows the turbo to spool up quickly and provide good acceleration response. At higher engine speeds, the turbo geometry changes such that exhaust gas flow into the turbo is not as restricted. In this configuration, more exhaust can flow through the turbocharger without causing an over-speed condition. The advantage that VGTs offer compared to a waste-gated turbocharger is that all exhaust flow is directed through the turbocharger under all operating conditions. This can be viewed as maximizing the use of the available exhaust energy.

b. Turbo Boost Control System Monitoring Requirements

We are proposing that the OBD system monitor the boost pressure control system on engines so equipped for under and over boost malfunctions. For engines equipped with variable geometry turbochargers (VGT), the OBD system would have to monitor the VGT system for slow response malfunctions. For engines equipped with charge air cooler systems, the OBD system would have to monitor the charge air cooler system for cooling system performance malfunctions. The individual electronic components (e.g., actuators, valves, sensors) that are used in the boost pressure control system shall be monitored in accordance with the comprehensive component requirements in section II.D.4.

i. Turbo Underboost Malfunctions

We are proposing that the OBD system detect a malfunction of the boost pressure control system prior to a decrease from the manufacturer's commanded boost pressure that would cause an engine's emissions to exceed the emissions thresholds for “other monitors” as shown in Table II.B-1. For engines in which no failure or deterioration of the boost pressure control system that causes a decrease in boost could result in an engine's emissions exceeding the applicable emissions thresholds, the OBD system must detect a malfunction when the system has reached its control limits such that it cannot increase boost to achieve the commanded boost pressure.

ii. Turbo Overboost Malfunctions

We are proposing that the OBD system detect a malfunction of the boost pressure control system prior to an increase from the manufacturer's commanded boost pressure that would cause an engine's emissions to exceed the emissions thresholds for “other monitors” as shown in Table II.B-1. For engines in which no failure or deterioration of the boost pressure control system that causes an increase in boost could result in an engine's emissions exceeding the applicable emissions thresholds, the OBD system must detect a malfunction when the system has reached its control limits such that it cannot decrease boost to achieve the commanded boost pressure.

iii. VGT Slow Response Malfunctions

We are proposing that the OBD system detect a malfunction prior to any failure or deterioration in the capability of the VGT system to achieve the commanded turbocharger geometry within a manufacturer-specified time that would cause an engine's emissions to exceed the emissions thresholds for “other monitors” as shown in Table II.B-1. For engines in which no failure or deterioration of the VGT system response could result in an engine's emissions exceeding the applicable emissions thresholds, the OBD system must detect a malfunction of the VGT system when proper functional response

of the system to computer commands does not occur.

iv. Turbo Boost Feedback Control Malfunctions

We are proposing that, for engines equipped with feedback control of the boost pressure system—e.g., control of VGT position, turbine speed, manifold pressure—the OBD system shall detect a malfunction when and if:

• The system fails to begin feedback control within a manufacturer specified time interval;

• A failure or deterioration causes open loop or default operation; or

• Feedback control has used up all of the adjustment allowed by the manufacturer.

v. Charge Air Undercooling Malfunctions

We are proposing that the OBD system detect a malfunction of the charge air cooling system prior to a decrease from the manufacturer's specified cooling rate that would cause an engine's emissions to exceed the emissions thresholds for “other monitors” as shown in Table II.B-1. For engines in which no failure or deterioration of the charge air cooling system that causes a decrease in cooling performance could result in an engine's emissions exceeding the applicable emissions thresholds, the OBD system must detect a malfunction when the system has no detectable amount of charge air cooling.

c. Turbo Boost Control System Monitoring Conditions

We are proposing that the OBD system monitor continuously for underboost and overboost malfunctions and for boost feedback control malfunctions. Manufacturers would be required to define the monitoring conditions for VGT slow response malfunctions such that the minimum performance ratio requirements discussed in section II.E would be met with the exception that monitoring must occur every time the monitoring conditions are met during the driving cycle in lieu of once per driving cycle as required for most monitors. For purposes of tracking and reporting as required in section II.E, all monitors used to detect VGT slow response malfunctions malfunctions must be tracked separately but reported as a single set of values as discussed in section II.E.

d. Turbo Boost MIL Illumination and DTC Storage

We are proposing the general MIL illumination and DTC storage requirements as discussed in section II.A.2.

5. Non-Methane Hydrocarbon (NMHC) Converting Catalyst Monitoring

a. Background

Diesel oxidation catalysts (DOCs) have been used on some nonroad diesel engines since the 1960s and on some diesel trucks and buses in the U.S. since the early 1990s. DOCs are generally used for converting HC and carbon monoxide (CO) emissions to water and CO

via an oxidation process. Current DOCs can also be used to convert PM emissions. DOCs may also be used in conjunction with other aftertreatment emission controls—such as NO

adsorber systems, selective catalytic reduction (SCR) systems, and PM filters—to improve their performance and/or clean up certain reducing agents that might slip through the system (e.g., the urea used in urea SCR systems).

b. NMHC Converting Catalyst Monitoring Requirements

We are proposing that the OBD system monitor the NMHC converting catalyst(s) for proper NMHC conversion capability. We are also proposing that each catalyst that converts NMHC be monitored either individually or in combination with others. For engines equipped with catalyzed diesel particulate filters (CDPFs) that convert NMHC emissions, the catalyst function of the CDPF must be monitored in accordance with the CDPF monitoring requirements in section II.B.8.

i. NMHC Converting Catalyst Conversion Efficiency

We are proposing that the OBD system detect an NMHC catalyst malfunction when the catalyst conversion capability decreases to the point that NMHC emissions exceed the emissions thresholds for “NMHC catalysts” as shown in Table II.B-1. If no failure or deterioration of the catalyst NMHC conversion capability could result in an engine's NMHC emissions exceeding the applicable emissions thresholds, the OBD system would have to detect a malfunction when the catalyst has no detectable amount of NMHC conversion capability.

ii. Other Aftertreatment Assistance Functions

For catalysts used to generate an exotherm to assist CDPF regeneration, we are proposing that the OBD system detect a malfunction when the catalyst is unable to generate a sufficient exotherm to achieve that regeneration. For catalysts used to generate a feedgas constituency to assist SCR systems (e.g., to increase NO

concentration upstream of an SCR system), the OBD system would have to detect a malfunction when the catalyst is unable to generate the necessary feedgas constituents for proper SCR system operation. For catalysts located downstream of a CDPF and used to convert NMHC emissions during a CDPF regeneration event, the OBD system would be required to detect a malfunction when the catalyst has no detectable amount of NMHC conversion capability.

c. NMHC Converting Catalyst Monitoring Conditions

Manufacturers would be required to define the monitoring conditions for NMHC converting catalyst malfunctions such that the minimum performance ratio requirements discussed in section II.E would be met. For purposes of tracking and reporting as discussed in section II.E, all monitors used to detect NMHC converting catalyst malfunctions must be tracked separately but reported as a single set of values as discussed in section II.E.

d. NMHC Converting Catalyst MIL Illumination and DTC Storage

We are proposing the general requirements for MIL illumination and DTC storage discussed in section II.A.2. Note that the monitoring method for the catalyst(s) must be capable of detecting all instances, except diagnostic self-clearing, when a catalyst DTC has been cleared but the catalyst has not been replaced (e.g., catalyst over temperature histogram approaches are not acceptable).

For gasoline catalyst monitoring, manufacturers generally use what is called an exponentially

weighted moving average (EWMA) approach to making decisions about the catalyst's pass/fail status. This approach monitors the catalyst and “saves” that information. The next time it monitors the catalyst, it saves that information along with the previous information, placing a higher weighting on the most recent information. This is done every time the OBD system monitors the catalyst and the EWMA saves six or seven monitoring events before making a decision. Importantly, once there exists six or seven pieces of information, every monitoring event can result in a decision because the EWMA is always using the previous six or seven events. Unfortunately, if a service technician clears the data with a scan tool, it is going to take six or seven monitoring events before the catalyst monitor can make a decision on the pass/fail status of the catalyst. So, we want to be sure that, in addition to the EWMA aspect of the catalyst monitor, there exists a way of determining quickly that someone has cleared the data but perhaps did not actually repair the catalyst. This is required to help prevent against DTC clearing without fixing a failed catalyst as a means of passing an inspection & maintenance test.

6. Selective Catalytic Reduction (SCR) and Lean NO

Catalyst Monitoring

a. Background

Selective Catalytic Reduction (SCR) catalysts that use ammonia as a NO

reductant have been used for stationary source NO

control for a number of years. Frequently, urea is used as the source of ammonia for SCR catalysts, and such systems are commonly referred to as Urea SCR systems. In recent years, considerable effort has been invested in developing urea SCR systems that could be applied to heavy-duty diesel vehicles with low sulfur diesel fuel. We now expect that urea SCR systems will be introduced in Europe to comply with the EURO IV heavy-duty diesel emission standards. Such systems have been introduced in the past year by some heavy-duty diesel engine manufacturers both in Europe and in Japan.

SCR catalyst systems require an accurate urea control system to inject precise amounts of reductant. An injection rate that is too low may result in lower NO

conversions while an injection that is too high may release unwanted ammonia emissions—referred to as ammonia slip—to the atmosphere. In general, ammonia to NO

ratios of around 1:1 are used to provide the highest NO

conversion rates with minimal ammonia slip. Therefore, injecting just the right amount of ammonia appropriate for the amount of NO

in the exhaust is very important. This can be challenging in a highway application because on-road diesel engines operate over a variety of speeds and loads. This makes the use of closed-loop feedback systems for reductant metering very attractive. This can be achieved, for example, with a dedicated NO

sensor in the exhaust so that the NO

concentration can be accurately known. With an accurate fast response NO

sensor, closed-loop control of the ammonia injection can be used to achieve and maintain the desired ammonia/NO

ratios in the SCR catalyst for the high NO

conversion efficiencies necessary to achieve the 2010 emission standards under various engine operating conditions.

Some have estimated that achieving the 2010 NO

emission standards with SCR systems will require NO

sensors that can measure NO

levels accurately in the 20 to 40 ppm range with little cross sensitivity to ammonia. Some in industry have even stated a desire for accuracy in the two to three ppm range. Suppliers have been developing NO

sensors capable of measuring NO

in the 0 to 100 ppm range with +/−5 ppm accuracy which we believe will be available by 2010.

Regarding cross-sensitivity to ammonia, work has been done that indicates ammonia and NO

measurements can be independently measured by conditioning the output signal.

This signal conditioning method resulted in a linear output for both ammonia and NO

from the NO

sensor downstream of the catalyst.

Draft Technical Support Document, HDOBD NPRM, EPA420-D-06-006, Docket ID# EPA-HQ-OAR-2005-0047-0008.

Schaer, C. M., Onder, C. H., Geering, H. P., and Elsener, M., “Control of a Urea SCR Catalytic Converter System for a Mobile Heavy-Duty Diesel Engine,” SAE Paper 2003-01-0776 which may be obtained from Society of Automotive Engineers International, 400 Commonwealth Dr., Warrendale, PA, 15096-0001.

For SCR systems, closed-loop control of the reductant injection may require the use of two NO

sensors. The first NO

sensor would be located upstream of the catalyst and the reductant injection point would be used for measuring the engine-out NO

emissions and determining the amount of reductant injection needed to reduce emissions. The second NO

sensor located downstream of the catalyst would be used for measuring the amount of ammonia and NO

emissions exiting the catalyst and providing feedback to the reductant injection control system. If the downstream NO

sensor detects too much NO

emissions exiting the catalyst, the control system can inject higher quantities of reductant. Conversely, if the downstream NO

sensor detects too much ammonia slip exiting the catalyst, the control system can decrease the amount of reductant injection.

In addition to exhaust NO

levels, another important parameter for achieving high NO

conversion rates with minimum ammonia slip is catalyst temperature. SCR catalysts have a defined temperature range where they are most effective. For example, platinum catalysts are effective between 175 and 250 degrees Celsius, vanadium catalysts are effective between 300 and 450 degrees Celsius, and zeolite catalysts are most effective between 350 and 600 degrees Celsius. To determine exhaust catalyst temperature for reductant control purposes, manufacturers are likely to use temperature sensors placed in the exhaust system. We project that only one temperature sensor positioned just downstream of the SCR system will be utilized for reductant injection control purposes.

Production SCR catalyst systems may also contain auxiliary catalysts to improve the overall emissions control capability of the system. An oxidation catalyst is often positioned downstream of the SCR catalyst to help control ammonia slip on systems without closed-loop control of ammonia injection. The use of a “guard” catalyst could allow higher ammonia injection levels, thereby increasing the NO

conversion efficiency without releasing un-reacted ammonia into the exhaust. The guard catalyst can also reduce HC and CO emission levels and diesel odors. However, increased N2O emissions may occur and NO

emission levels may actually increase if too much ammonia is oxidized in the catalyst. Some SCR systems may also include an oxidation catalyst upstream of the SCR catalyst and urea injection point to generate NO2 for lowering the effective operating temperature and/or volume of the SCR catalyst. Studies have indicated that increasing the NO2 content in the exhaust stream can reduce the SCR temperature requirements by about 100 degrees Celsius.

This “pre-oxidation” catalyst also has the added benefit of reducing HC emissions.

Walker, A. P., Chandler, G. R., Cooper, B. J., et al., “An Integrated SCR and Continuously Regenerating Trap System to Meet Future NO

and PM Legislation,” SAE Paper 2000-01-0188 which may be obtained from Society of Automotive Engineers International, 400 Commonwealth Dr., Warrendale, PA, 15096-0001.

b. SCR and Lean NO

Catalyst Monitoring Requirements

We are proposing that the OBD system monitor SCR catalysts and lean NO

catalysts for proper conversion capability. We are also proposing that each catalyst that converts NO

be monitored either individually or in combination with others. For engines equipped with SCR systems or other catalyst systems that utilize an active/intrusive reductant injection (e.g., active lean NO

catalysts utilizing diesel fuel

injection), the OBD system would be required to monitor the active/intrusive reductant injection system for proper performance. The individual electronic components (e.g., actuators, valves, sensors, heaters, pumps) in the active/intrusive reductant injection system must be monitored in accordance with the comprehensive component requirements in section II.D.4.

i. Catalyst Conversion Efficiency Malfunctions

We are proposing that the OBD system detect a catalyst malfunction when the catalyst conversion capability decreases to the point that would cause an engine's NO

emissions to exceed any of the applicable emissions thresholds for “NO

Catalyst Systems” as shown in Table II.B-1. If no failure or deterioration of the catalyst NO

conversion capability could result in an engine's NO

emissions exceeding any of the applicable emissions thresholds, the OBD system would have to detect a malfunction when the catalyst has no detectable amount of NO

conversion capability.

ii. Active/Intrusive Reductant Injection System Malfunctions

Specific to SCR and other active/intrusive reductant injection system performance, we are proposing that the OBD system detect a malfunction prior to any failure or deterioration of the system to regulate reductant delivery properly (e.g., urea injection, separate injector fuel injection, post injection of fuel, air assisted injection/mixing) that would cause an engine's NO

emissions to exceed any of the applicable emissions thresholds for “NO

Catalyst Systems” as shown in Table II.B-1. As above, if no failure or deterioration of the reductant delivery system could result in an engine's NO

emissions exceeding the applicable emissions thresholds, the OBD system would have to detect a malfunction when the system has reached its control limits such that it is no longer able to deliver the desired quantity of reductant.

If the system uses a reductant other than the fuel used for the engine or uses a reservoir/tank for the reductant that is separate from the fuel tank used for the engine, the OBD system must detect a malfunction when there is no longer sufficient reductant available (e.g., the reductant tank is empty). If the system uses a reservoir/tank for the reductant that is separate from the fuel tank used for the engine, the OBD system must detect a malfunction when an improper reductant is used in the reductant reservoir/tank (e.g., the reductant tank is filled with something other than the proper reductant).

iii. SCR and Lean NO

Catalyst Feedback Control System Malfunctions

If the engine is equipped with feedback control of the reductant injection, we are proposing that the OBD system detect a malfunction when and if:

• The system fails to begin feedback control within a manufacturer specified time interval;

• A failure or deterioration causes open loop or default operation; or

• Feedback control has used up all of the adjustment allowed by the manufacturer.

c. SCR and Lean NO

Catalyst Monitoring Conditions

Manufacturers would be required to define the monitoring conditions for catalyst conversion efficiency malfunctions such that the minimum performance ratio requirements discussed in section II.E would be met. For purposes of tracking and reporting as required in section II.E, all monitors used to detect catalyst conversion efficiency malfunctions must be tracked separately but reported as a single set of values as specified in section II.E.

We are also proposing that the OBD system monitor continuously for active/intrusive reductant injection system malfunctions. Manufacturers would be required to monitor continuously the active/intrusive reductant delivery system.

d. SCR and Lean NO

Catalyst MIL Illumination and DTC Storage

We are proposing the general MIL illumination and DTC storage requirements presented in section II.A.2 with the exception of active/intrusive reductant injection related malfunctions. If the OBD system is capable of discerning that a system malfunction is being caused by an empty reductant tank, the manufacturer may delay illumination of the MIL if the vehicle is equipped with an alternative indicator for notifying the vehicle operator of the malfunction. The manufacturer would be required to demonstrate that: The alternative indicator is of sufficient illumination and location to be readily visible to the operator under all lighting conditions; and the alternative indicator provides equivalent assurance that a vehicle operator will be promptly notified; and, that corrective action would be undertaken. If the vehicle is not equipped with an alternative indicator and the MIL illuminates, the MIL may be immediately extinguished and the corresponding DTC erased once the OBD system has verified that the reductant tank has been properly refilled and the MIL has not been illuminated for any other type of malfunction. The Administrator may approve other strategies that provide equivalent assurance that a vehicle operator will be promptly notified and that corrective action will be undertaken.

The monitoring method for the catalyst(s) would have to be capable of detecting all instances, except diagnostic self-clearing, when a catalyst DTC has been cleared but the catalyst has not been replaced (e.g., catalyst over temperature histogram approaches are not acceptable).

7. NO

Adsorber System Monitoring

a. Background

adsorbers, or lean NO

traps (LNT), work to control NO

emissions by storing NO

on the surface of the catalyst during the lean engine operation typical of diesel engines and then by undergoing subsequent brief rich regeneration events where the NO

is released and reduced across a precious metal catalyst.

adsorber systems generally consist of a conventional three-way catalyst function (e.g., platinum) with NO

storage components (i.e., adsorbents) incorporated into the washcoat. Three-way catalysts convert NO

emissions as well as HC and CO emissions (hence the name three-way) by promoting oxidation of HC and CO to H

O and CO

using the oxidation potential of the NO

pollutant and, in the process, reducing the NO

emissions to nitrogen, N

. Said another way, three-way catalysts work with exhaust conditions where the net oxidizing and reducing chemistry of the exhaust is approximately equal, allowing the catalyst to promote complete oxidation/reduction reactions to the desired exhaust components of CO

, H

O, and N

. The oxidizing potential in the exhaust comes from NO

emissions and any feedgas oxygen (O

) not consumed during combustion. The reducing potential in the exhaust

comes from HC and CO emissions, which represent products of incomplete combustion. Operation of the engine to ensure that the oxidizing and reducing potential of the combustion and exhaust conditions is precisely balanced is referred to as stoichiometric engine operation.

Because diesel engines run lean of stoichiometric operation, the NO

emissions are stored, or absorbed—via chemical reaction with alkaline earth metals such as barium nitrate in the washcoat—and then released during rich operation for conversion to N

. This NO

release during rich operation is referred to as a regeneration event. The rich operating conditions required for NO

regeneration, which generally last for several seconds, are typically achieved using a combination of intake air throttling (to reduce the amount of intake air), exhaust gas recirculation, and post-combustion fuel injection.

adsorber systems have demonstrated NO

reduction efficiencies from 50 percent to in excess of 90 percent. This efficiency has been found to be highly dependent on the fuel sulfur content because NO

adsorbers are extremely sensitive to sulfur. The NO

adsorption material has an even greater affinity for sulfur compounds than NO

. Thus, sulfur compounds can saturate the adsorber and limit the number of active sites for NO

adsorption, thereby lowering the NO

reduction efficiency. Accordingly, low sulfur fuel is required to achieve the greatest NO

reduction efficiencies. Although new adsorber washcoat materials are being developed with a higher resistance to sulfur poisoning and ultra-low sulfur fuel will be the norm by 2010, NO

adsorber systems will still need to purge the stored sulfur from the storage bed by a process referred to as desulfation. Because the desulfation process takes longer (e.g., several minutes) and requires more fuel and heat than the NO

regeneration step, permanent thermal degradation of the NO

adsorber and fuel economy penalties may result from desulfation events happening with excessive frequency. However, if desulfation is not done frequently enough, NO

storage capacity would be compromised and fuel economy penalties would be incurred from excessive attempts at NO

regeneration.

In order to achieve and maintain high NO

conversion efficiencies while limiting negative impacts on fuel economy and driveability, vehicles with NO

adsorber systems will require precise air/fuel control in the engine and in the exhaust stream. Diesel manufacturers are expected to utilize NO

sensors and temperature sensors to provide the most precise closed-loop control for the NO

adsorber system. If NO

sensors are not used to control the NO

adsorber system, manufacturers could use wide-range air-fuel (A/F) sensors located upstream and downstream of the adsorber as a substitute. However, A/F sensors cannot provide an instantaneous indication of tailpipe NO

levels, which would allow the control system to precisely determine when the adsorber system is filled to capacity and regeneration should be initiated. If A/F sensors are used in lieu of NO

sensors, an estimation of engine-out NO

emissions and their subsequent storage in the NO

adsorber can be achieved indirectly through modeling.

b. NO

Adsorber System Monitoring Requirements

We are proposing that the OBD system monitor the NO

adsorber on engines so equipped for proper performance. For engines equipped with active/intrusive injection (e.g., in-exhaust fuel and/or air injection) to achieve NO

regeneration, the OBD system would have to monitor the active/intrusive injection system for proper performance. The individual electronic components (e.g., injectors, valves, sensors) that are used in the active/intrusive injection system would have to be monitored in accordance with the comprehensive component requirements in section II.D.4.

i. NO

Adsorber Capability Malfunctions

We are proposing that the OBD system detect a NO

adsorber malfunction when its capability—i.e., its combined adsorption and conversion capability—decreases to the point that would cause an engine's NO

emissions to exceed the applicable emissions thresholds for “NO

Catalyst Systems” as shown in Table II.B-1. If no failure or deterioration of the NO

adsorber capability could result in an engine's NO

emissions exceeding the applicable emissions thresholds, the OBD system would have to detect a malfunction when the system has no detectable amount of NO

adsorber capability.

ii. Active/Intrusive Reductant Injection System Malfunctions

For NO

adsorber systems that use active/intrusive injection (e.g., in-cylinder post fuel injection, in-exhaust air-assisted fuel injection) to achieve desorption of the NO

adsorber, the OBD system would have to detect a malfunction if any failure or deterioration of the injection system's ability to properly regulate injection causes the system to be unable to achieve desorption of the NO

adsorber.

iii. NO

Adsorber Feedback Control System Malfunctions

If the engine is equipped with feedback control of the reductant injection (e.g., feedback control of injection quantity, time), we are proposing that the OBD system detect a malfunction when and if:

• The system fails to begin feedback control within a manufacturer specified time interval;

• A failure or deterioration causes open loop or default operation; or

• Feedback control has used up all of the adjustment allowed by the manufacturer.

c. NO

Adsorber System Monitoring Conditions

We are proposing that manufacturers define the monitoring conditions for NO

adsorber capability malfunctions such that the minimum performance ratio requirements discussed in section II.E would be met. For purposes of tracking and reporting as required in section II.E, all monitors used to detect NO

adsorber capability malfunctions must be tracked separately but reported as a single set of values as specified in section II.E.

We are also proposing that the OBD system monitor continuously for active/intrusive reductant injection and feedback control system malfunctions.

d. NO

Adsorber System MIL Illumination and DTC Storage

We are proposing the general requirements for MIL illumination and DTC storage discussed in section II.A.2.

8. Diesel Particulate Filter (DPF) System Monitoring

a. Background

Diesel particulate filters control diesel PM by capturing the soot (solid carbon) portion of PM in a filter media, typically a ceramic wall flow substrate, and then by oxidizing (burning) it in the oxygen-rich atmosphere of diesel exhaust.

In aggregate over a driving cycle, the PM must be burned at a rate equal to or

greater than its accumulation rate, or the DPF will clog. Given low sulfur diesel fuel (diesel fuel with a sulfur content of 15 ppm or lower), highly active catalytic metals (e.g., platinum) can be used to promote soot oxidation. This method of PM filter regeneration, called passive regeneration, is the primary means of soot oxidation that we project industry will use in 2007/2010.

See “Regulatory Impact Analysis: Heavy-Duty Engine and Vehicle Standards and Highway Diesel Fuel Sulfur Control Requirements;” EPA420-R-00-026; December 2000 at Chapter III for a more complete description of DPFs.

The DPF technology has proven itself in tens of thousands of retrofit applications where low sulfur diesel fuel is already available. More than a million light-duty passenger cars in Europe now have diesel particulate filters. DPFs are considered the most effective control technology for the reduction of particulate emissions and can typically achieve PM reductions in excess of 90 percent.

In order to maintain the performance of the DPF and the engine, the trapped PM must be periodically removed before too much particulate is accumulated and exhaust backpressure reaches unacceptable levels. The process of periodically removing accumulated PM from the DPF is known as “regeneration” and is very important for maintaining low PM emission levels. DPF regeneration can be passive (i.e., occur continuously during regular operation of the filter), active (i.e., occur on a controlled, periodic basis after a predetermined quantity of particulates have been accumulated), or a combination of the two. With passive regeneration, the oxidizing catalyst material on the DPF substrate serves to lower the temperature for oxidizing PM. This allows the DPF to continuously oxidize trapped PM material during normal driving. In contrast, active systems utilize an external heat source—such as an electric heater or fuel burner—to facilitate DPF regeneration. We are projecting that virtually all DPF systems will have some sort of active regeneration mechanism as a backup mechanism should operating conditions not be conducive for passive regeneration.

One of the key considerations for a DPF regeneration control system is the amount of soot quantity that is stored in the DPF (often called soot loading). If too much soot is stored when regeneration is activated, the soot can burn uncontrollably and DPF substrate could be damaged via melting or cracking. Conversely, activating regeneration when there is too little trapped soot will not ensure good combustion propagation which would effectively waste the energy (fuel) used to initiate the regeneration. Another important consideration in the control system design is the fuel economy penalty involved with DPF regeneration. Prolonged operation with high backpressures in the exhaust and regenerations occurring too frequently are both detrimental to fuel economy and DPF durability. Therefore, DPF system designers will need to carefully balance the regeneration frequency with various conflicting factors. To optimize the trap regeneration for these design factors, the DPF regeneration control system is projected to incorporate both pressure sensors and temperature sensors to model soot loading and other phenomena.

Through the information provided by these sensors, designers can optimize the DPF for high effectiveness and maximum durability while minimizing fuel economy and performance penalties.

Salvat, O., Marez, P., and Belot, G., “Passenger Car Serial Application of a Particulate Filter System on a Common Rail Direct Injection Diesel Engine,” SAE Paper 2000-01-0473 which may be obtained from Society of Automotive Engineers International, 400 Commonwealth Dr., Warrendale, PA, 15096-0001.

b. DPF System Monitoring Requirements

We are proposing that the OBD system monitor the DPF on engines so-equipped for proper performance.

For engines equipped with active regeneration systems that utilize an active/intrusive injection (e.g., in-exhaust fuel injection, in-exhaust fuel/air burner), the OBD system would have to monitor the active/intrusive injection system for proper performance. The individual electronic components (e.g., injectors, valves, sensors) that are used in the active/intrusive injection system must be monitored in accordance with the comprehensive component requirements in section II.D.4.

Note that these requirements would also apply to a catalyzed diesel particulate filter (CDPF). We use the more common term DPF throughout this discussion.

i. PM Filtering Performance

We are proposing that the OBD system detect a malfunction prior to a decrease in the filtering capability of the DPF (e.g., cracking, melting, etc.) that would cause an engine's PM emissions to exceed the applicable emissions thresholds for “DPF Systems” as shown in Table II.B-1. If no failure or deterioration of the PM filtering performance could result in an engine's PM emissions exceeding the applicable emissions thresholds, the OBD system would have to detect a malfunction when no detectable amount of PM filtering occurs.

ii. DPF Regeneration Frequency Malfunctions—Too Frequent

We are proposing that the OBD system detect a malfunction when the DPF regeneration frequency increases from—i.e., occurs more often than—the manufacturer's specified regeneration frequency to a level such that it would cause an engine's NMHC emissions to exceed the applicable emissions threshold for “DPF Systems” as shown in Table II.B-1. If no such regeneration frequency exists that could cause NMHC emissions to exceed the applicable emission threshold, the OBD system would have to detect a malfunction when the PM filter regeneration frequency exceeds the manufacturer's specified design limits for allowable regeneration frequency.

iii. DPF Incomplete Regeneration Malfunctions

We are proposing that the OBD system detect a regeneration malfunction when the DPF does not properly regenerate under manufacturer-defined conditions where regeneration is designed to occur.

iv. DPF NMHC Conversion Efficiency Malfunctions

We are proposing that, for any DPF that serves to convert NMHC emissions, the OBD system must monitor the NMHC converting function of the DPF and detect a malfunction when the NMHC conversion capability decreases to the point that NMHC emissions exceed the NMHC threshold for “DPF Systems” as shown in Table II.B-1. If no failure or deterioration of the NMHC conversion capability could result in NMHC emissions exceeding the applicable NMHC threshold, the OBD system would have to detect a malfunction when the system has no detectable amount of NMHC conversion capability.

v. DPF Missing Substrate Malfunctions

We are proposing that the OBD system detect a malfunction if either the DPF substrate is completely destroyed, removed, or missing, or if the DPF assembly has been replaced with a muffler or straight pipe.

vi. DPF Active/Intrusive Injection System Malfunctions

We are proposing that, for systems that utilize active/intrusive injection (e.g., in-cylinder post fuel injection, in-exhaust air-assisted fuel injection) to achieve DPF regeneration, the OBD system detect a malfunction if any

failure or deterioration of the injection system's ability to properly regulate injection causes the system to be unable to achieve DPF regeneration.

vii. DPF Regeneration Feedback Control System Malfunctions

We are proposing that, if the engine is equipped with feedback control of the DPF regeneration (e.g., feedback control of oxidation catalyst inlet temperature, PM filter inlet or outlet temperature, in-cylinder or in-exhaust fuel injection), the OBD system must detect a malfunction when and if:

• The system fails to begin feedback control within a manufacturer specified time interval;

• A failure or deterioration causes open loop or default operation; or

• Feedback control has used up all of the adjustment allowed by the manufacturer.

c. DPF System Monitoring Conditions

We are proposing that manufacturers define the monitoring conditions for all DPF related malfunctions such that the minimum performance ratio requirements discussed in section II.E would be met with the exception that monitoring must occur every time the monitoring conditions are met during the driving cycle rather than once per driving cycle as required for most monitors. For purposes of tracking and reporting as required in section II.E, all monitors used to detect all DPF related malfunctions would have to be tracked separately but reported as a single set of values as specified in section II.E.

For specific components or systems that have multiple monitors that are required to be reported (e.g., exhaust gas sensor bank 1 may have multiple monitors for senso

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