LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Cadillac >> 2002 >> Escalade EXT >> Repair and Diagnosis >> External Pages >> Different car >> Section 468 (Charging System) >> Diagnostic Tests >> DTC P1637: Output Driver Module Malfunction >> Diagnostic Procedure
April 5, 2026: LEMON Manuals is launched! Read the announcement.

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.
  1. If diagnostic system check was not performed, go to ENGINE ELECTRICAL DIAGNOSTIC SYSTEM CHECK  under ON-VEHICLE TESTING. If diagnostic system check was performed, go to next step.
  2. Connect scan tool to Data Link Connector (DLC). DLC is located under instrument panel, near steering column. Turn ignition switch to RUN position. Using scan tool, command charge indicator light ON and OFF. If light responds to each command, problem is intermittent. Check wiring and connections. If light does not respond to each command, go to next step.
  3. Turn ignition switch to LOCK position. Disconnect Instrument Panel Cluster (IPC) connector. Turn ignition switch to RUN position. Connect a test light between IPC battery positive voltage circuit (terminal No. 1) and a good ground. See WIRING DIAGRAMS  . If test light illuminates, go to next step. If test light does not illuminate, go to step  10 .
  4. Connect a test light between IPC battery positive voltage circuit (terminal No. 1) and IPC charge indicator control circuit. See WIRING DIAGRAMS  . Using scan tool, command charge indicator light ON and OFF. If indicator responds to each command, go to step  8 . If indicator does not respond to each command, go to next step.
  5. If test light remains illuminated during test performed in step  4 , go to step  7 . If test light does not illuminate, go to next step.
  6. Test IPC charge indicator control circuit for a short to voltage or an open. See WIRING DIAGRAMS  . Repair circuit as necessary, then go to step  13 . If open or short to voltage was not found, go to step  9 .
  7. Test IPC charge indicator control circuit for a short to ground. See WIRING DIAGRAMS  . Repair circuit as necessary, then go to step  13 . If short to ground was not found, go to step  9 .
  8. Inspect IPC for poor connections. Repair as necessary, then go to step  13 . If connections are okay, go to step  11 .
  9. Inspect PCM for poor connections. Repair as necessary, then go to step  13 . If connections are okay, go to step  12 .
  10. Repair charge indicator battery positive voltage circuit, then go to step  13 .
  11. Replace charge indicator light. Go to step  13 .
  12. Replace PCM. After replacement, reprogram PCM. See REMOVAL & INSTALLATION article in ENGINE PERFORMANCE. Go to next step.
  13. Using scan tool, clear DTCs. Turn ignition on. If DTC P1637 resets, go to step  2 . If DTC P1637 does not reset, system is okay.
scientia non olet · About LEMON Manuals