Interpretation ID: nht76-3.45
DATE: 03/12/76
FROM: AUTHOR UNAVAILABLE; R. B. Dyson; NHTSA
TO: Rockwell International
TITLE: FMVSS INTERPRETATION
TEXT: This responds to Rockwell International's February 17, 1976, question whether the addition by a manufacturer of a computer power relay unit (CPR) to an antilock system already installed on a vehicle in satisfaction of Standard No. 121, Air Brake Systems, is prohibited by @ 108(a)(2) of the National Traffic and Motor Vehicle Safety Act (15 U.S.C. @ 1397(a)(2)). Section 108(a)(2) provides that, with one exception, no manufacturer, distributor, dealer, or repair business shall knowingly render inoperative, in whole or part, any device or element of design installed on or in a motor vehicle in compliance with an applicable Federal motor vehicle safety standard. As you describe the CPR function, it is added to a functioning antilock system to sense improper electrical signals and to prevent them from causing the antilock system to release the brakes when they should remain applied. The CPR acts by discontinuing power to the antilock system and warning the driver.
Section 108(a)(2) has been construed by the NHTSA to apply to situations where a system installed in compliance with a safety standard is defeated so that it no longer possesses the performance capabilities considered necessary by the agency and set forth in its standards. The agency has determined that some modifications can be made (e.g., substitution of a bumper that meets current requirements in place of a bumper that meets earlier requirements) as long as the performance required by the standard is met. In the case of your CPR, the issue is whether the addition of a device that shuts off the antilock function under some malfunction circumstances would be considered "knowingly [rendering] inoperative" an element of Standard No. 121.
As you describe the CPR function, it would not. As in other standards, Standard No. 121 contemplates failure of the regulated system and provides for the safest operation of the system under such circumstances. For example, the standard calls for low-air and antilock-failure warning signals (S5.1) and for uninterrupted operation of the air brake system in the event of electrical failure in the antilock system (S5.5). Antilock manufacturers have also provided logic circuits in their systems to sense certain malfunctions and take corrective action. The fact that the Rockwell CPR is additional protection against malfunction that is being added to systems already installed is not a significant distinction. From your description, the CPR does not defeat the designed performance called for by Standard No. 121, and its installation by a manufacturer would not constitute a violation of @ 108(a)(2).
YOURS TRULY,
February 17, 1976
National Highway Traffic Safety Administration
Attention: Office of Defects Investigation
Subject: Rockwell SKID-TROL(R) Request for Interpretation
Under the date of July 10, 1975, Rockwell International wrote to NHTSA advising of a safety related anti-lock problem that existed on some units. Also included in that letter (copy attached) was a reference to a Rockwell developed in-vehicle diagnostic aid that would enhance the operation and safety of the wheel anti-lock device.
This unit is known as the Computer Power Relay (CPR Unit) and its function is to detect unwanted intermittent signals that may be encountered due to mechanical problems, such as loose wheel bearings or misadjusted wheel end parts.
A more detailed description of its function is as follows:
* The CPR unit has been designed to operate in conjunction with Rockwell's SKID-TROL(R) wheel anti-lock system and detects improper sensor-to-rotor gap as soon as it occurs without the brakes being applied. Further, it gives the operator warning of the condition and returns the vehicle to the manual braking mode. A return to manual braking occurs when the unit detects an abnormal solenoid switching that occurs before the brake pedal is depressed. If such a condition should occur, the CPR removes the power to all wheel anti-lock units on the vehicle until the unit is purposely reset and the condition causing the abnormal switching is corrected.
Since July 1975, the unit has been regularly installed with Rockwell SKID-TROL(R) systems with successful results. We have, however, been asked by a customer as to conflict with Sec. 103 (2) (A) of the Safety Act, Public Law 93-492, which reads in part "No manufacturer, distributor, dealer, or motor vehicle repair business shall knowingly render inoperative, in whole or part, any device or element of design installed on or in a motor vehicle or item of motor vehicle equipment in compliance with an applicable Federal motor vehicle safety standard."
The effect of the CPR unit is the same as that of the normal fail-safe portion of an anti-lock device, except that it has the added advantages of detecting unwanted intermittent signals and is resetable.
In any event, Rockwell International would appreciate NHTSA's interpretation that the unit does not conflict with Sec. 103, paragraph (2) (A) of the Safety Act.
ROCKWELL INTERNATIONAL CORPORATION AUTOMOTIVE OPERATIONS
G. J. Flannery Director - Government Relations
ATTACH.
July 10, 1975
National Highway Traffic Safety Administration
Attention: Office of Defects Investigation
Attached is a copy of our letter to vehicle manufacturers in connection with a safety related wheel anti-lock problem that exists on some units in use and could exist in the future as the result of misassembly in maintenance. Also attached is a listing of vehicle manufacturers to whom this notice has been sent.
The wheel anti-lock system is performing as designed and the malfunction results from mechanical causes rather than electrical. It is expected that the individual vehicle manufacturers receiving this notice will advise NHTSA of the actual number of units released to the field. Rockwell International estimates that the major number of suspect units were assembled during the first few weeks of production of FMVSS #121 type units. A cutoff date of July 1, 1975 has been established to insure that all suspect units are corrected. Rockwell International will advise NHTSA of the total units shipped to vehicle manufacturers as soon as it is available.
Included in the attached notification is a recommendation that wheel bearings should be properly adjusted and wheel ends checked with a Service Aid Tester after maintenance.
Rockwell International has also developed in-vehicle diagnostic equipment that will be available in the near future that detects mechanical problems affecting the wheel anti-lock system.
Rockwell International will, in the interest of highway safety, provide this diagnostic equipment without charge to operators for use in conjunction with Rockwell International wheel anti-lock systems unitl they can be incorporated into new production vehicles.
Rockwell International will continue to make an all out effort to assist vehicle manufacturers in remedying the problem contained in the attached notification.
ROCKWELL INTERNATIONAL CORPORATION AUTOMOTIVE OPERATIONS
G. J. Flannery Director - Government Relations