Interpretation ID: 23871.jeg

Mr. Philip M. Headley
Chief Engineer, Advanced Technologies
Continental Teves
4141 Continental Drive
Auburn Hills, MI 48326

Dear Mr. Headley:

This responds to your request for an interpretation of Federal Motor Vehicle Safety Standard No. 135. You stated that Continental Teves has developed a system which uses the ABS hydraulic pump to supplement the driver's braking effort in the event of a vacuum booster failure. The system is able to recognize the booster failure and meter hydraulic fluid from the ABS pump to the wheel brakes in response to the driver's pedal force. You are concerned, however, that the driver may not recognize that the vacuum boost failure has occurred, since the brakes may appear to operate normally. Consequently, the driver may not have the vacuum booster problem repaired. A subsequent malfunction of the ABS system could then render the vehicle unable to meet the failed boost requirements of Standard No. 135.

You stated that you believe the prudent action in this case would be to light the brake telltale to alert the driver of the problem. You asked whether this would be permissible under Standard No. 135, given that booster failure is not one of the specified conditions for which the brake telltale is required to be illuminated. As discussed below, the answer to your question is yes.

By way of background, the National Highway Traffic Safety Administration (NHTSA) does not provide approvals of motor vehicles or motor vehicle equipment. Under 49 U.S.C. Chapter 301, manufacturers are required to ensure that their vehicles and equipment meet applicable requirements. The following represents our opinion based on the facts you provided in your letter.

As you noted in your letter, we have previously addressed a similar question from General Motors (GM) in the context of the requirements of Standard No. 105. (Letter to Stephen E. Selander, Esq., dated April 29, 1992.) S5.3.1 of that standard required a brake telltale to illuminate when there was a gross loss of hydraulic pressure (or, alternatively, a drop in fluid level), a total functional electrical failure in the antilock or variable proportioning brake system, and when the parking brake was applied. GM stated that a brake telltale on a planned vehicle would illuminate under these prescribed conditions. That company indicated, however, that a diagnostic capability would also exist to detect other faults in the brake system, and requested the agency's concurrence that S5.3.1 permitted illumination of the brake telltale when other faults were detected which increased the likelihood of a substantial degradation in brake system performance.

We noted that while Standard No. 105 required that a brake telltale be provided which activated under certain specified conditions, it did not expressly state whether the required telltale may also be activated under other conditions. We provided our opinion that the telltale may also activate under other conditions so long as such activation does not obscure or confuse the meaning of the required telltale or otherwise defeat its purpose.

We noted that the purpose of the brake telltale was to warn the driver of one of two conditions: (1) the parking brake was applied (and hence should be released before driving), or (2) the brake system had a significant fault which should be corrected. Since the additional conditions for activation which GM contemplated would represent significant brake system faults which should be corrected, it was our opinion that activation of the brake telltale under such conditions would not in any way defeat the purpose of the brake telltale.

We believe the rationale of our interpretation to GM is directly applicable to the question you ask about the very similar brake telltale requirements of Standard No. 135.

S5.5 of Standard No. 135 requires one or more brake telltales to be provided which activate under two types of specified conditions: (1) the parking brake is applied, and (2) the brake system has a significant fault which should be corrected. Since the additional condition for which Continental Teves contemplates activation of the brake telltale also represents a significant fault in the brake system which should be corrected, it is our opinion that activation under that condition would not in any way defeat the purpose of the brake telltale, and is permissible under Standard No. 135.

I hope this information is helpful. If you have any further questions, please call Edward Glancy of my staff at (202) 366-2992.

Sincerely,

Jacqueline Glassman
Chief Counsel
ref:135
d.5/30/02