Anti-Lock Brake System: Operation

As vehicle is moving, speed sensors send AC signals to ECU. ECU monitors brakelight switch to determine when brake pedal is pressed. When brake pedal is pressed, ECU monitors signals from each speed sensor to determine rate of deceleration.

If rate of deceleration from any speed sensor reaches a preprogrammed rate, ECU activates solenoid valves inside actuator. Solenoid valves are cycled to apply, release or maintain hydraulic pressure to each wheel in any combination.

Regulating hydraulic pressure to each circuit prevents wheel lock-up. When brake pedal is released, ECU deactivates solenoid valves, returning brake system to conventional mode until ABS is needed.

If ECU detects a fault, ANTI-LOCK warning light on the instrument cluster comes on. ECU deactivates ABS when a fault is detected, but conventional brake system is not affected.