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
As vehicle is moving, each wheel speed sensor sends an AC signal to the ECU. When brake pedal is applied, ECU receives signal through stoplight switch. When this occurs, ECU will monitor deceleration rate of wheels through wheel speed sensors. One sensor is located on each wheel.
If deceleration rate from any speed sensor reaches a preprogrammed rate, ECU activates solenoid valves inside actuator (electro-hydraulic unit). Solenoid valves are cycled to apply, release or maintain hydraulic pressure to each brake caliper depending upon signals from ECU. Regulating hydraulic pressure to each caliper prevents wheel lock-up.
When brake pedal is released, ECU will deactivate solenoid valves, and system will return to conventional brake system operation until ABS is again needed.
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.
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