Anti-Lock Brake System: Operation

As vehicle is moving, speed sensors send an AC signal to ECU. ECU monitors the stoplight switch to determine when driver presses brake pedal. 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 driver releases brake pedal, ECU deactivates solenoid valves, placing brake system back into a conventional mode until ABS is again needed.

If a fault is detected by ECU, an ANTI-LOCK light located on the instrument panel illuminates. Although ECU deactivates ABS when a fault is detected, conventional brake system is not be affected.