Jeep Wrangler/YJ 1987-1995 Repair Guide

Description and Operation


See Figure 1

The Teves Anti-lock Brake System (ABS) is an electronically operated, all wheel brake control system that became available on the Wrangler beginning in 1993. The major components include the master cylinder, vacuum power brake booster, Electronic Control Unit (ECU), Hydraulic Control Unit (HCU) and various control sensors.

The anti-lock system is designed to retard wheel lockup during periods of high wheel slip when braking. Retarding wheel lockup is accomplished by modulating fluid pressure to the wheel brake units.

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Fig. Fig. 1: Anti-lock brake system schematic

The ABS electronic control system is separate from other electrical circuits in the vehicle. A specially programmed ECU is used to operate the system components. The system components include the following:

Electronic Control Unit (ECU)
Wheel speed sensors and axle shaft tone rings
Hydraulic Control Unit (HCU)
Tandem master cylinder with central valves
Vacuum power brake unit
Pedal travel sensor
Acceleration switch
Main relay and pump motor relay
ABS warning light
Pump motor sensor

ABS components not repairable and are serviced as assemblies only. The axle shaft tone rings are not serviceable. If a tone ring becomes damaged, it will be necessary to replace the axle shaft.

Wheel brake components (such as the calipers, brake shoes, wheel cylinders, rotors and drums) are all serviced in the same manner as standard brake system components.