Anti-Lock Brake System: Operation

As vehicle is driven, each wheel speed sensor sends an AC signal to ABS ECU. As brake pedal is depressed, ABS ECU starts to monitor vehicle rate of deceleration. If rate of deceleration is greater than preprogrammed amount, ABS ECU signals hydraulic control unit solenoid valves to regulate brake hydraulic pressure. Solenoid valves increase or decrease hydraulic pressure to each front wheel and/or to both rear wheels. This action will slow each wheel at a preprogrammed rate to prevent wheel lock-up, allowing driver to maintain steering control.

If ABS malfunction occurs, ABS warning light will come on in instrument cluster panel. ABS ECU will then deactivate ABS system, leaving conventional braking system intact. ABS ECU can also self-diagnose ABS during each ignition cycle (OFF-ON-OFF). If an ABS fault is detected, ABS ECU will store a trouble code to assist technician in diagnosing ABS.