Diagnosis & Testing: Notes

WARNING: This page is about a different car, the 1999 GMC Sierra and 1999 Chevrolet Silverado. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: When testing and diagnosing 4WAL system, use of Tech 2 scan tool is required.

The Electronic Brake Control Module (EBCM) constantly monitors for faults. The EBCM detects and isolates system failures, then sets the corresponding Diagnostic Trouble Code (DTC).

Before diagnosing 4WAL system, perform a comprehensive visual inspection of system by checking wiring harness connectors, 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 using DIAGNOSTIC SYSTEM CHECK. If failures are found when performing DIAGNOSTIC SYSTEM CHECK, you will be directed to enter diagnostics to retrieve DTCs or perform SYMPTOM TESTS. DIAGNOSTIC SYSTEM CHECK may indicate that system is functioning properly.