1991 Corvette: Service Bulletin: ABS Pump Noisy / "ABS Active" Light Flashes

Subject: ANTI-LOCK BRAKE SYSTEM (ABS) PUMP MAKES NOISE AND "ABS ACTIVE" LIGHT FLASHES WHILE DRIVING
Model and Year: 1991 CORVETTE
Source: Chevrolet Service Bulletin
Bulletin Number: 91-491A-5 - (06/01/1992)

THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN NO. 91-491-5, DATED MARCH 1992. A NEW PART NUMBER HAS BEEN ADDED. ALL COPIES OF 91-491-5 SHOULD BE DISCARDED.

Condition: The ABS (Anti-Lock Brake System) pump may run for one second, and the "ABS Active" light may flash, five minutes after starting the vehicle. The customer may describe this as "the motor runs by itself and the light flashes while driving". The customer may also notice that the "ABS Active" light may not flash when the vehicle reaches 4 mph (7 km/hr.)

Cause: During a normal vehicle start, the ABS goes thru a self-diagnostic test, which includes running the motor and flashing the "ABS Active" light for one second. This normally occurs when the vehicle reaches 4 mph (7km/hr). However, if the voltage drops below 9.4 volts while cranking the engine, the ABS self-test will stop, and will reset itself to repeat the test five minutes after the voltage goes above 10 volts.

Correction: To address customer concerns, a revised ABS EBCM (Electronic Brake Control Module) P/N 10223326 has been released for service, which changes the reset time from five MINUTES to five SECONDS.

Part Availability:

Parts are currently available from GMSPO.

Warranty Information:

Labor Operation: H2505

Use applicable labor time guide for labor hours.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.