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Speedometer Is Inaccurate

  1. If diagnostic system check has been performed, go to next step. If diagnostic system check has not been performed, perform INSTRUMENT CLUSTER DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM.
  2. Road test vehicle and observe speedometer. If speedometer does not indicate correct speed, go to next step. If speedometer indicates correct speed, problem may be intermittent. Try to recreate fault by wiggling wiring and connectors. Check for faulty connections at all connectors that may be causing intermittent condition. See WIRING DIAGRAMS  .
  3. Disconnect Powertrain Control Module connectors. On 3.8L, connect a 10-amp fused jumper wire between ground and terminal No. 55 (Dark Green/White wire) at PCM C1 connector. See Figure . On 5.7L, connect a 10-amp fused jumper wire between ground and terminal No. 50 (Dark Green/White wire) at PCM C2 connector. See Figure . On all models, disconnect instrument cluster connector. Connect a test light between terminals B8 (Dark Green/White wire) and A3 (Pink wire) at instrument cluster connector. See Figure . Turn ignition on. If test light does not illuminate, go to step  5 . If test light illuminates, go to next step.
  4. Check for faulty connections at PCM and instrument cluster connectors. Repair as necessary. Recheck system operation. If connectors are okay, replace instrument cluster. See INSTRUMENT CLUSTER  under REMOVAL & INSTALLATION.
  5. Repair open or poor connection in Dark Green/White wire between PCM connector and instrument cluster connector. Repair as necessary. Recheck system operation.
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