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 - 4WAL: Operation
When ignition is turned on, ABS and BRAKE warning lights will illuminate for 2 seconds, then turn off as bulb check. EBCM performs self-check of 4WAL system, once each ignition cycle, when vehicle speed reaches 8 MPH. If faults are detected, ABS indicator light will illuminate (in most cases) and 4WAL functions will be disabled. A related Diagnostic Trouble Code (DTC) will be stored. The BRAKE light illuminates if parking brake is applied or a mechanical brake problem is detected.
When brake pedal is depressed, brake switch voltage to PCM/VCM drops from 12 volts to one volt. At this point, PCM/VCM monitors wheel speed through an AC signal generated by speed sensors located at each wheel. If the deceleration rate of wheel speed reaches a preprogrammed rate, PCM/VCM will activate various control valves to prevent wheel lock-up by increasing or decreasing hydraulic pressure to each channel: left front, right front or rear wheels.
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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.