Antilock Brakes / Traction Control Systems: Description and Operation

4 Wheel Anti-Lock Brake System (4WABS) System Outline
^ During vehicle operation, including normal and antilock braking, the 4WABS control module monitors all electrical anti-lock functions and some hydraulic operations.
^ When the brakes are applied, brake fluid is sent through four normally open solenoid valves contained inside the ABS hydraulic unit to each wheel.
^ If the control module senses a wheel is about to lock, it will prevent any more fluid from entering that wheel circuit.
^ Once the affected wheel comes back up to speed, the 4WABS control module returns the valves to their normal condition allowing fluid to flow to the affected brake.
^ When the ignition is turned to RUN, the yellow ABS warning indicator will appear for three seconds as part of a system self-check.
^ A malfunction in the system will cause the 4WABS control module to shut off or inhibit the system. However, normal power-assisted braking remains. Malfunctions are indicated by a yellow ABS warning indicator in the instrument cluster.