Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2001CHEVY EXPRESS G3500, VAN PASSENGER EXTENDED, 6.5 FREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 300 (CHARGING SYSTEM)DIAGNOSTIC TESTSDTC P1637: OUTPUT DRIVER MODULE MALFUNCTIONDIAGNOSTIC PROCEDURE
2001 Chevrolet Chevy Express G3500, Van Passenger Extended, 6.5 F
Diagnostic Procedure
2001 Chevrolet Chevy Express G3500, Van Passenger Extended, 6.5 FSECTION Diagnostic Procedure
WARNING: This page is about a different car, the 2002 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.
- 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.
- 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.
- 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 .
- 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.
- 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.
- 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 .
- 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 .
- Inspect IPC for poor connections. Repair as necessary, then go to step 13 . If connections are okay, go to step 11 .
- Inspect PCM for poor connections. Repair as necessary, then go to step 13 . If connections are okay, go to step 12 .
- Repair charge indicator battery positive voltage circuit, then go to step 13 .
- Replace charge indicator light. Go to step 13 .
- Replace PCM. After replacement, reprogram PCM. See REMOVAL, OVERHAUL & INSTALLATION article in ENGINE PERFORMANCE. Go to next step.
- 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.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.