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Speedometer Inoperative/Inaccurate: Testing

  1. Connect scan tool. Using scan tool, check for PCM DTCs. If DTC P0500 is set, PCM is not able to accurately read vehicle speed signal. See TESTS W/CODES article in ENGINE PERFORMANCE section.
  2. Using scan tool, check data for IPD03 (vehicle speed to IPC). If scan tool displays zero and DTC P0500 is not set, malfunction is between IPC and PCM. Using DVOM, check voltage at IPC Blue 24-pin connector C1, terminal B5 (Dark Green wire). Voltage should be pulsed. Repair as necessary. Recheck system operation.
  3. If IPD03 is displaying correct vehicle speed, IPC is receiving and processing vehicle speed information correctly, but is not displaying the information properly. Check for poor connections at IPC connectors. If connections are okay, replace IPC. See procedures in INSTRUMENT PANEL CLUSTER (IPC)  under REMOVAL & INSTALLATION. Perform IPC DIAGNOSTIC SYSTEM CHECK  under DIAGNOSTIC TESTING.
  4. If IPD03 is fluctuating with speedometer gauge, check for poor terminal contact at all electrical connections. If problem is intermittent, wiggle wires to duplicate conditions at time of malfunction. Check for proper routing of circuit No. 817 (Dark Green wire) between IPC connector C1, terminal B5 and PCM Clear 80-pin connector C2, terminal No. 25.
  5. If vehicle speed always reads 8 percent faster than actual speed, IPC may be operating in export mode. Go to SPEED DISPLAY HIGHER THAN ACTUAL SPEED .
  6. Erratic speedometer and tachometer displays can be caused by loose or intermittent PCM ground connections. Check for poor connections at PCM and engine ground. Repair as necessary. Recheck system operation.
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