General Motors; Grant of Application for Decision of Inconsequential Noncompliance

DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

[Docket No. NHTSA 98-4075]

General Motors; Grant of Application for Decision of

Inconsequential Noncompliance

General Motors Corporation (GM) of Warren, Michigan, determined

that some of its 1997 model Chevrolet Corvettes failed to meet the

requirements of Federal Motor Vehicle Safety Standard (FMVSS) No. 124,

``Accelerator Control Systems,'' and filed an appropriate report

pursuant to 49 CFR Part 573, ``Defects and Noncompliance Reports.'' GM

also applied to be exempted from the notification and remedy

requirements of 49 U.S.C. Chapter 301--``Motor Vehicle Safety'' on the

basis that the noncompliance is inconsequential to motor vehicle

safety.

Notice of receipt of the application was published on September 16,

1997, and an opportunity afforded for comment (Docket No. 97-58, Notice

1; 62 FR 48708).

Paragraph S5.2 of FMVSS No. 124 requires the throttle to return to

idle position within the time limits specified in S5.3, whenever any

component of the accelerator control system is disconnected or severed

at a single point. S5.3 requires return to idle within 3 seconds for

any vehicle exposed to temperatures of 0 degrees to -40 degrees F (-18

degrees to -40 degrees C). During the 1997 model year, GM produced

9,500 Chevrolet Corvettes, which will not comply with FMVSS No. 124

because, when tested with one return spring removed at temperatures

below -26 degrees F, their accelerator pedal module assembly does not

move quickly enough to cause the throttle to return to the idle

position within 3 seconds.

GM described the noncompliance and supported its application with

the following arguments:

The Chevrolet Corvette employs an electronic throttle control which

adjusts the throttle position based on input from the accelerator pedal

position. The accelerator pedal is equipped with three springs, any two

of which are capable of returning the pedal to rest position. Once this

occurs, the throttle returns to idle position approximately 0.2 seconds

later. A test run in early May, however, raised a question about the

ability of the pedal assembly to return at low temperatures.

GM believes that the failure of the pedal assembly to meet the

throttle closing time requirements of FMVSS No. 124 at extremely low

temperatures is inconsequential to motor vehicle safety for the

following reasons.

1. Vehicle Controllability--In the unlikely event that all of the

prerequisites necessary for the noncompliance occurred--that is, a

return spring was disconnected or severed on a pedal assembly with

residual oil, and the vehicle soaked at ambient temperatures below -32

degrees C--the vehicle would continue to be controllable both by the

service brakes and as a result of the Brake Torque Management System.

2. Reliability of the Accelerator Springs--The condition which is

the subject of GM's noncompliance decision can only occur if one of the

return springs is severed or disconnected. The springs in the Corvette

pedal assembly, however, have extremely high reliability and are not

likely to fail in the real world.

3. Condition Requires Extreme Temperatures; Pedal Assembly Warms

Quickly--As mentioned above, the root cause of the noncompliance

condition is the residual oil on the pedal assemblies congealing below

-32 degrees C. Testing at temperatures above that level resulted in

full compliance with the FMVSS No. 124 time limits for all pedal

assemblies tested. Therefore, the ambient temperatures required for the

possibility of this noncompliance to exist are severe. Even if a

vehicle with a disconnected return spring soaked under the necessary

harsh conditions for a sufficient time to congeal the residual oil, the

potential for the noncompliance to occur would exist for only a short

time, because the pedal assembly would warm up quickly with activation

of the vehicle heating system.

4. Condition is Self-correcting--Durability testing indicates that

the condition improves with wear. Bench testing was conducted on five

production pedal assemblies with poor

[[Page 41321]]

return times. The pedals on these assemblies were cycled at room

temperature. Since the vast majority of driving is done with a only

limited pedal movement, each cycle consisted of a 10 per cent

application of pedal travel. Every 2,000 cycles the pedal return at -40

degrees F (-40 degrees C) was checked. The results, shown in Figure 5

[of the application], indicate that most pedals will return within the

specified time limit after 10,000 cycles, and all pedals will easily

meet the time limits after 15,000 cycles.

5. Warranty Data--GM has reviewed recent warranty data for the 1997

Corvette, as well as complaint data. We are unaware of any data

suggesting the subject condition is a real world safety issue.

No comments were received on the application.

FMVSS No. 124 requires that the accelerator control system return

to the idle position in the event of a single point disconnection or

severance of the system in no more than three seconds after the pedal

is released when tested at temperatures from -18 degrees C (0 degrees

F) to -40 degrees C (-40 degrees F also). If the severance is of one of

the three pedal return springs inside the passenger compartment, full

return will take longer than three seconds when the temperature of the

passenger compartment is below -32 degrees C (-26 degrees F).

In this instance, there are many mitigating circumstances that

render the noncompliance inconsequential to safety. First, the

noncompliance does not result in the throttle sticking open at extreme

low temperatures. It merely closes more slowly as a result of congealed

lubricant on a new pedal assembly with tightly fitting parts. (GM

determined that the lubricant was not necessary for long term

durability or corrosion protection and discontinued its use to avoid

further non-compliances.) Even with one return spring removed, the

accelerator pedal returns at least 85 percent of full travel within the

specified time. The worst consequence is merely the duration of an

elevated idle speed for about six seconds, and the vehicle is subject

to this condition only for periods when the temperature in the

passenger compartment is below -26 degrees F. Second, the pedal

assemblies loosen up enough in about 2000 miles of normal driving to

correct the noncompliance. While pedal assemblies with all three return

springs satisfy the performance requirements of FMVSS No. 124 under all

temperature conditions regardless of congealed lubrication or tight fit

of parts, even those with one spring removed will satisfy the standard

after about 2,000 miles of use despite the congealed lubrication at -40

degrees F. It is unlikely that many of the first 9,500 1997 Corvettes,

which had lubricated pedal assemblies, have not yet corrected

themselves. Third, it is extremely unlikely that a pedal return spring

would fail during the first 2000 miles of driving. The springs are

designed for an infinite fatigue life, and they are mounted in a

protected area. Also, they are direct acting compression springs not

dependent upon connections.

In consideration of the foregoing, it is hereby found that General

Motors Corporation has met its burden of persuasion that the

noncompliance discussed herein is inconsequential to motor vehicle

safety, and its application is granted.

(49 U.S.C. 30118 and 30120; delegations of authority at 49 CFR 1.50 and

501.8)

Issued on: July 28, 1998.

L. Robert Shelton,

Associate Administrator for Safety Performance Standards.

[FR Doc. 98-20654 Filed 7-31-98; 8:45 am]

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