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Home >> GMC >> 1998 >> Forward Control 6.5 F >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes - Introduction >> Self-Diagnostic System >> DLC Diagnosis Or No Scan Tool Data >> 2.2L & 2.4L

2.2L & 2.4L

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . After performing OBD system check, go to next step.
  2. Turn ignition on, with engine off. If MIL illuminates, go to next step. If MIL does not illuminate, go to MIL INOPERATIVE .
  3. Connect scan tool. If scan tool powers up, go to next step. If scan tool does not power up, go to step  6.
  4. Using scan tool, attempt to communicate with Body Control Module (BCM) and Electronic Brake Control Module (EBCM). If scan tool communicates with both control modules, go to step  11. If scan tool does not communicate with both control modules, go to next step.
  5. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on, with engine off. Using scan tool, attempt to communicate with BCM and EBCM. If scan tool communicates with both control modules, go to step  13. If scan tool does not communicate with both control modules, go to step  12.
  6. Using a DVOM, measure voltage between ground and DLC battery feed circuit at DLC. See appropriate wiring diagram in WIRING DIAGRAMS article. If voltage is near battery voltage, go to next step. If voltage is not as specified, go to step  8.
  7. Using a DVOM, measure voltage between battery positive and both DLC ground circuits at DLC. See appropriate wiring diagram in WIRING DIAGRAMS article. If voltage is near battery voltage at both circuits, go to step  9. If voltage is not as specified, go to step  10.
  8. Repair poor connection, open or short to ground in battery feed circuit. After repairs, go to step  17.
  9. Check for open battery feed fuse and poor connections at DLC. Repair as necessary. After repairs, go to step  17. If no problem is found, go to step  14.
  10. Repair open or poor connections in DLC ground circuits. After repairs, go to step  17.
  11. Check class 2 serial data line for an open or poor connection between PCM and circuit splice. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step  17. If circuit is okay, go to step  13.
  12. Check class 2 serial data line for an open, short to power, short to ground or poor connection between PCM and DLC. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step  17. If circuit is okay, go to step  14.
  13. Turn ignition off. Replace PCM. Perform PCM relearn procedures. After repairs, go to step  16.
  14. Install scan tool on another vehicle equipped with class 2 serial data and check for proper operation. If scan tool operates properly, go to appropriate TROUBLE SHOOTING - NO CODES article. If scan tool does not operate properly, go to next step.
  15. Scan tool is malfunctioning. Refer to scan tool manufacturer's instructions. After repairs, go to step  17.
  16. Ensure PCM and CKP relearn procedures were performed if PCM was replaced. Attempt to start engine. If engine starts and continues to run, go to next step. If engine does not start, or starts and then stalls, go to step  2.
  17. Allow engine to reach normal operating temperature. Using scan tool, check for DTCs. If DTCs are present, diagnose DTCs. See DIAGNOSTIC TESTS in appropriate TESTS W/CODES article. If DTCs are not present, system is okay.
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