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Home >> Pontiac >> 2003 >> Vibe Base, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Self-Diagnostics >> Diagnostic Tests >> DTC P0500: VSS Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Raise and support drive wheels. Support lower control arms so drive axles are in a horizontal position. Start and idle engine. Observe VEHICLE SPEED parameter on scan tool. Allow engine to idle in gear with drive wheels rotating. Does scan tool parameter indicate a vehicle speed? If yes, go to next step. If no, go to step  4.
  3. Using scan tool, store DTC freeze frame information. Use scan tool to clear DTCs. Place vehicle into CHECK MODE using scan tool. Operate vehicle within freeze frame conditions. Does DTC P0500 set? If yes, go to next step. If no, go to DIAGNOSTIC AIDS .
  4. Observe speedometer with engine at idle in gear with drive wheels rotating. Does speedometer indicate a vehicle speed? If yes, go to step  10. If no, go to next step.
  5. Do all other instrument cluster assembly functions operate normally? If yes, go to next step. If no, go to INSTRUMENT PANEL - VIBE article in ACCESSORIES & EQUIPMENT.
  6. Turn ignition OFF. Disconnect VSS harness connector. Turn ignition switch to RUN position, engine OFF. Probe VSS connector terminal No. 1 on harness side using a test light connected to ground. Does test light illuminate? If yes, go to next step. If no, go to step  12.
  7. Using a test light connected to battery voltage, probe VSS harness connector terminal No. 2. Does test light illuminate? If yes, go to next step. If no, go to step  13.
  8. With a test light connected to battery voltage, probe VSS harness connector terminal No. 3 (harness side). Does test light illuminate? If yes, go to step  14. If no, go to next step.
  9. Reconnect VSS connector. Disconnect Instrument Panel Cluster (IPC) harness connector. Set-up Digital Multimeter (DMM) to measure the DC frequency on speedometer vehicle speed input circuit terminal No. 18. Start and idle engine. Allow engine to idle in gear with drive wheels rotating. Does DMM indicate a frequency? If yes, go to step  18. If no, go to step  15.
  10. Turn ignition switch to OFF position. Disconnect PCM harness White 35-pin connector C3, containing the vehicle speed input terminal. Turn ignition switch to RUN position, engine OFF. Probe vehicle speed input circuit terminal on harness side with DMM connected to ground. Measure DC voltage on the vehicle speed input circuit. Is the voltage 9-12 volts? If yes, go to next step. If no, go to step  16.
  11. Set-up the DMM to measure DC frequency on PCM vehicle speed input circuit. Start and idle engine. Allow engine to idle in gear with drive wheels rotating. Does DMM indicate a frequency? If yes, go to step  20. If no, go to step  17.
  12. Repair cause of no power to VSS connector. After repair, go to step  21.
  13. Repair cause of no ground to VSS connector. After repair, go to step  21.
  14. Check speedometer vehicle speed input circuit for a short to ground. Repair as necessary. Was a repair necessary? If yes, go to step  21. If no, go to step  18.
  15. Check speedometer vehicle speed input circuit for an open. Repair as necessary. Was a repair necessary? If yes, go to step  21. If no, go to step  19.
  16. Check PCM vehicle speed input circuit for a short to ground or open. If equipped, ensure cruise control module is not shorted internally. See CRUISE CONTROL SYSTEMS - VIBE article in ACCESSORIES & EQUIPMENT. Repair as necessary. Was a repair necessary? If yes, go to step  21. If no, go to step  18.
  17. Check PCM vehicle speed input circuit for a short to battery voltage. Repair as necessary. Was a repair necessary? If yes, go to step  21. If no, go to step  18.
  18. Replace speedometer. After repair, go to step  21.
  19. Replace VSS. After repair, go to step  21.
  20. Replace PCM. After repair, go to next step.
  21. Use scan tool to clear DTCs and road test vehicle within freeze frame conditions that set the DTC. Review scan tool data and check for DTCs. Repair is complete if no DTCs are stored. Are any DTCs displayed on scan tool? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay at this time.
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