Anti-Lock Brake System: Operation

The EBCM is located behind glove box. Wheel speed sensors relay information about wheel acceleration, deceleration and slip value to EBCM. The EBCM controls braking by activating and deactivating electromagnetic modulator valve.

The modulator valve consists of 3 rapidly switching solenoid valves, accumulator chamber and a return pump. The valves increase and decrease brake fluid pressure to each wheel (rear wheels are one circuit) to prevent wheel lock-up.

The modulator valve can supply only as much fluid pressure as applied by the driver through the master cylinder. The modulator valve alone CANNOT apply the brakes.

As a quick system test: When ignition switch is turned to RUN position, Amber ANTI-LOCK warning light on instrument panel will illuminate. After engine is started, light goes out with battery warning light. If ABS warning light fails to go out or comes on while driving, a system fault is indicated.

ABS systems are under high pressure under normal operating conditions. Before opening the fluid reservoir or before servicing any component of an ABS system, it is mandatory that system pressure be discharged. To discharge system, turn ignition off and pump brake pedal a minimum of 20-25 times using full pedal strokes. When a definite increase in pedal effort is felt, pump pedal 2 more times.