Diagnosis & Repair Procedure
NOTE:
For better performance and results of this diagnostic procedure, usage of appropriate wiring diagram is recommended. See ENGINE PERFORMANCE
in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
NOTE:
Perform all voltage and resistance tests using a Digital Volt-Ohmmeter (DVOM) with a minimum 10-megohm input impedance, unless stated otherwise in test procedure. Use an ohmmeter to isolate wiring harness shorts or opens.
- Turn ignition switch to ON position. If other instrument cluster indicators and warning lights illuminate, go to next step. If other instrument cluster indicators and warning lights do not illuminate, check the following:
- Check IG fuse (20-amp).
- Check Main fuse (80-amp).
- Check for open or short in Black/White wire between IG fuse and instrument cluster.
- Check for poor, loose, corroded or damaged terminal connections in fuse box, junction block and instrument cluster harness connectors.
If problem is found repair as necessary and retest system for normal operation.
- Start engine. If engine starts, go to next step. If engine does not start, check ECM ground and power supply. See C: ENGINE CONTROL MODULE POWER & GROUND CIRCUIT CHECK . After repair, retest system for normal operation.
- Turn ignition switch to LOCK position. Disconnect ECM harness connectors. See Figure. Check for poor, loose, corroded or damaged ECM harness connector terminals. If connector terminals are okay, leave harness connectors disconnected and go to next step. If connector terminals are faulty, repair as necessary and retest system for normal operation.
- Using a fused jumper wire, ground ECM harness connector G04 terminal No. 4 (Purple/Yellow wire). See Fig 1. Turn ignition switch to ON position. If MIL illuminates, substitute ECM with a known good unit and retest system for normal operation. If MIL does not illuminate, check for faulty MIL bulb. If MIL bulb is faulty, replace as necessary. If MIL bulb is okay, repair open or short circuit in Purple/Yellow wire between instrument cluster and ECM. After repair, retest system for normal operation.