LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> GMC >> 2000 >> C3500 HD 6.5 F, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics - Diesel >> Circuit Tests >> Malfunction Indicator Light Inoperative
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Malfunction Indicator Light Inoperative

  1. Perform OBD system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
  2. Attempt to start engine. If engine starts, go to next step. If engine does not start, go to step  6.
  3. Check GAUGES fuse No. 4 (10-amp) located in instrument panel fuse block. If fuse is okay, go to next step. If fuse is open, go to step  14.
  4. Turn ignition on. Using test light connected to ground, probe ignition feed circuit at instrument cluster connector. If test light illuminates, go to next step. If test light does not illuminate, go to step  11.
  5. Turn ignition off. Disconnect 32-pin PCM harness connector (Blue). Turn ignition on. Connect fused jumper wire between ground and MIL control circuit of PCM harness connector. If MIL illuminates, go to step  9. If MIL does not illuminate, go to step  10.
  6. Check fuses to PCM ignition and battery feed circuits. If fuses are okay, go to next step. If fuse(s) are open, go to step  13.
  7. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Using test light connected to ground, probe ignition and battery feed circuits at PCM harness connector. If test light illuminates on both circuits, go to next step. If test light does not illuminate on both circuits, go to step  12.
  8. Check for poor PCM ground connections. Repair as necessary. After repairs, go to step  20. If ground connections are okay, go to next step.
  9. Check for poor PCM harness connections. Repair as necessary. After repairs, go to step  20. If connections are okay, go to step  15.
  10. Check for open in MIL control circuit. Repair as necessary. After repairs, go to step  20. If circuit is okay, go to step  16.
  11. Repair open in ignition feed circuit to instrument cluster. After repairs, go to step  20.
  12. Locate and repair open in PCM battery feed or ignition circuit. Repair as necessary. After repairs, go to step  20.
  13. Locate and repair short to ground in PCM ignition feed circuit or PCM battery feed circuit. Repair as necessary. After repairs, go to step  20.
  14. Locate and repair short to ground in instrument cluster ignition feed circuit. After repairs, go to step  20.
  15. Replace PCM. Perform PCM relearn procedures. See PROGRAMMING . After repairs, go to step  20.
  16. Check MIL control circuit for poor connection at instrument cluster harness connector. Repair as necessary. After repairs, go to step  20. If circuit connection is okay, go to next step.
  17. Remove instrument cluster assembly. Inspect MIL bulb. If bulb is okay, go to step  19. If bulb is faulty, go to next step.
  18. Replace MIL bulb. After repairs, go to step  20.
  19. Replace instrument cluster. After repairs, go to next step.
  20. Using scan tool, clear DTCs. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start, go to step  2.
  21. Allow engine to reach normal operating temperature. Using scan tool, check for DTCs. If any DTCs are set, perform appropriate DTC test. See DIAGNOSTIC TESTS . If no DTCs are set, go to next step.
  22. Using scan tool, check for any DTCs that have not been diagnosed. If undiagnosed DTCs are displayed, perform appropriate DTC test. See DIAGNOSTIC TESTS . If no DTCs are displayed, system is okay.
scientia non olet · About LEMON Manuals