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: Diagnosis: Notes
The Brake Pressure Modulator Valve (BPMV) contains a self-diagnostic capability to detect system failures. When a fault code is set, the BPMV may disable 4WAL system and illuminate ANTI-LOCK light for duration of ignition cycle. Fault codes stored by BPMV can be displayed using Tech 1 with appropriate cartridge.
Before diagnosing 4WAL system, perform a comprehensive visual inspection of system by checking wiring harness connectors for looseness and harness routing (pay particular attention to wheel speed sensor wiring harness routing), applicable fuses in fuse block and ground connections. Ensure brake fluid level in master cylinder reservoir is full.
Start 4WAL system diagnosis with FUNCTIONAL TEST under TROUBLE SHOOTING CHARTS . If failures are found during FUNCTIONAL TEST, you will be directed to enter diagnostics to retrieve codes or perform symptom diagnosis. FUNCTIONAL TEST may indicate 4WAL system is functioning properly.
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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.