Subject: INFO ON ABS NOISE - SELF TEST NORMAL AFTER IGNITION CYCLE
Model and Year:1989-91 CAPRICE, 1986-91 CORVETTE, 1990-91 WL VAN, 1991 S/T TRUCK (4-DOOR ONLY)
Source: Chevrolet Service Bulletin
Bulletin Number: 91-241-5 - (02/01/1991)
All anti-lock brake systems (ABS) perform a self-test called initialization during acceleration after each ignition switch cycle.
During this test, the modulator exercises valves/solenoids/motors as the system monitors all inputs and outputs. This test is initiated at a relatively low speed so the ABS can be deactivated in the event there is an abnormal condition detected. Depending on the application, initialization occurs at different speeds, (typically between 0-8 MPH) and will vary in intensity.
As it is possible to hear and feel the initialization cycle, some customers may comment about it. Initialization is a normal condition, therefore, repair should not be attempted.
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.
© Copyright General Motors Corporation. All Rights Reserved
Article ID: 641
Created: July 31, 2014
Last Updated: July 31, 2014
Online URL: https://www.corvetteactioncenter.com/tech/knowledgebase/article/1986-1991-corvette-service-bulletin-information-on-abs-noise-self-test-641.html