ABS PEDAL PULSATION NEW WHEEL SPEED SENSOR

SUBJECT: ABS BRAKE PEDAL PULSATION WHEN APPLYING BRAKES (NEW WHEEL SPEED SENSOR)

MODELS AFFECTED: 1991-1992 DE VILLES, FLEETWOODS, AND SIXTY SPECIALS

This bulletin is being revised to add 1992 model year; add new part number for wheel speed sensor; modify the condition, diagnosis, and correction sections; add warranty information; and supersedes bulletin T-91-97 which should be discarded.

Some 1991-1992 DeVille, Fleetwood, and Sixty Special owners may notice brake pedal vibration (ABS cycling) and the pedal may drop approximately one inch at the end of a brake stop. This usually happens when decelerating below 10 mph and the brakes are not applied hard enough and/or road conditions are not such to activate the AntiLock Brake System. VIN Breakpoints involved are:

1991 1992 ---- ---- DeVille/Fleetwood/ All DeVille/Fleetwood/ SOP-N4320770 Sixty Special Sixty Special

This condition may be caused by moisture intrusion into the rear wheel speed sensor. The pedal vibration (ABS cycling), due to moisture intrusion, may or may not set a diagnostic trouble code. Use a Tech I or CAMS to read any ABS diagnostic trouble codes that may be stored in the EBCM. Follow the Service Information Manual procedure to repair any stored diagnostic trouble codes.

If any of the rear ABS wheel speed sensor diagnostic trouble codes are stored or if no diagnostic trouble codes are stored, replace both rear wheel speed sensors, clear codes, and road test the vehicle before replacing any other AntiLock system component. A new rear wheel speed sensor kit, P/N 10457166 (one per box) has been released for service. This sensor can be distinguished from the previous (gray) sensor by the black color. Parts are currently available from GMSPO.

For warranty purposes use Labor Operation T5305 at 1.2 hours. Add .1 hour for wire wheel covers.

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.