BRAKE PEDAL PULSATION AT LOW SPEEDS

SUBJECT: BRAKE PEDAL PULSATION AT LOW SPEEDS (REPLACE REAR AXLE SPEED SENSOR)

VEHICLES AFFECTED: 1990-92 "D" MODELS

THIS BULLETIN SUPERSEDES AND REPLACES PRODUCT SERVICE BULLETIN 91-4-102 (DATED JAN. 31/91)(CADILLAC BULLETIN T91-26). THIS BULLETIN IS BEING REVISED TO INCLUDE THE 1992 MODEL YEAR.

Some 1990-92 Cadillac Broughams may experience slight brake pedal pulsation at speeds less than 24 kph (1 5 mph) and/or the intermittent setting of ABS codes 35 and/or 36 while braking to a stop. These conditions may be due to a damaged rear axle speed sensor or reluctor ring.

When diagnosing a vehicle with the above condition, remove the rear axle speed sensor from the differential housing and inspect the sensor for damage. If the sensor is damaged, remove the differential cover and inspect the ring gear, reluctor gear, and pinion for damage (i.e., gear chipping, mashing, wear, etc.). Replace any damaged parts.

NOTICE: If the reluctor gear is separated from the pinion for any reason, it must be replaced. The reluctor gear is attached to the pinion gear with a one-time press fit; it cannot be reused. Attempts to reuse the reluctor gear will result in slippage of the reluctor ring.

All 1990 and 1991 vehicles built after breakpoint 729879 have a new style rear axle speed sensor. When working on a Brougham built prior to the above breakpoint that exhibits one of the above conditions, replace the rear axle speed sensor with P/N 3525994 whether or not it shows evidence of damage. Use the following part numbers when replacing the rear axle speed sensor, reluctor ring and ring and pinion gears:

Rear Axle Speed Sensor: 3525994

Axle Option Reluctor Ring and No. of Teeth Ratio Code P/N Pinion On Reluctor ----- ------ -------- -------- ------------ 3.08 GU4 26018943 26031114 22 2.93 GW9 ('90 only) 26018938 26016282 ('90 only) GU3 2.73 GU2 ('90 only) 26018937 26017967 ('90 only) 25

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.