Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.