Anti-Lock Brake System: Operation

ABS Control Module (ACM) controls ABS operation. ACM receives and processes information from wheel speed sensors, brake switch, ignition switch and battery voltage through ABS enable relay. When wheel lock-up is about to occur, ACM activates Anti-Lock Brake Control Assembly (ABCA) components to modulate hydraulic pressure to each wheel. ABS incorporates self-diagnostic capabilities.

ABCA includes motor pack assembly, modulator assembly, solenoid valves and brake master cylinder. ABCA modulates brake hydraulic pressure when ACM determines wheel lock-up.

Wheel Speed Sensors (WSS) provide a frequency and voltage that is proportional to wheel speed. Signal is used by Anti-Lock Brake Control Module (ACM) to determine road wheel speed. Typical WSS output signals vary from 100 millivolts at low wheel speed to 90 volts at high wheel speed.