Anti-Lock Brake System: Description

An Anti-Lock Brake System (ABS) is used on Cherokee and Wagoneer models equipped with Selec-Trac 4WD. This electronically operated systems is designed to reduce wheel lock-up during heavy braking. System components consist of an Electronic Control Module (ECM), master cylinder/power booster unit, 4 wheel speed sensors, pump/motor assembly, 3 relays, 2 indicators lights, pressure modulator and an accumulator. See Figure .

On 1989-90 models, the ECM is equipped with a mercury switch. This switch monitors the amount of vehicle deceleration to determine what type of surface the vehicle is on. This allows the ECM to provide improved operation in 4WD mode on low traction road surface.