Test No. 4: Tachometer Inaccurate/Inoperative
- If instrument panel cluster diagnostic system check has been performed, go to next step. If instrument panel cluster diagnostic system check has not been performed, go to INSTRUMENT PANEL CLUSTER DIAGNOSTIC SYSTEM CHECK under SELF-DIAGNOSTIC SYSTEM.
- Turn ignition off. Connect scan tool to Data Link Connector (DLC). Turn ignition on. Select POWERTRAIN CONTROL MODULE (PCM) data list. Monitor ENGINE SPEED parameter. Test drive vehicle. If ENGINE SPEED parameter does not match tachometer reading, go to next step. If ENGINE SPEED parameter matches tachometer reading, check for intermittent poor connections at PCM and Instrument Panel Cluster (IPC) connectors.
- Check for open, short to ground, short to voltage or high resistance in White wire between PCM connector C1 terminal No. 56 and Instrument Panel Cluster (IPC) connector C1 terminal A5. See Figure and Figure . If circuit is okay, go to next step. If faulty circuit is found and repaired, go to step 6 .
- Check for poor connections at IPC connector terminals. If connections are okay, go to next step. If faulty connections are found and repaired, go to step 6 .
- Replace Instrument Panel Cluster (IPC). See INSTRUMENT PANEL CLUSTER (IPC) under REMOVAL & INSTALLATION. Using scan tool, obtain approximate mileage, and contact an authorized Delco service center for transfer of information from failed IPC to replacement IPC. After repairs, go to next step.
- Recheck operation of tachometer. If tachometer operates properly, repair is complete. If tachometer does not operate properly, go to step 2 .