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Home >> GMC >> 2003 >> Safari Van Cargo, AWD >> Repair and Diagnosis >> Engine Performance >> Testing & Diagnosis >> Engine Controls - Self-Diagnostics - 4.3L >> Diagnostic Tests >> DTC P0500: Vehicle Speed Sensor ("S" & "T" Series With M/T Only) >> Diagnostic Procedures

Diagnostic Procedures

  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
    2. WARNING: In order to avoid damage to the drive axles, support the lower control arms in the normal horizontal position. Do not run the vehicle in gear with the wheels hanging down at full travel.
    NOTE: Record the Failure Records before clearing the DTCs. Using the Clear Info function erases the Failure Records from the PCM.
  2. Install scan tool. Turn ignition on, with engine off. Record the DTC Freeze Frame and Failure Records. Clear the DTC. Raise the drive wheels. Start engine. Allow the engine to idle in gear. Does the scan tool display vehicle speed greater than zero MPH? If yes, go to next step. If no, go to step  4.
  3. Turn ignition off. Turn ignition on, with engine off. Review the Freeze Frame data and record the parameters. Start engine. Operate the vehicle within the Freeze Frame conditions and Conditions for Running DTC. See CONDITIONS FOR RUNNING DTC . Does the scan tool display vehicle speed greater than zero MPH? If yes, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 4.3L ASTRO, BLAZER, JIMMY CANADIAN, SAFARI, SONOMA & S10 PICKUP article. If no, go to next step.
  4. Verify that the latest calibration is installed in the PCM. Update the PCM with the latest calibration as necessary. Did the PCM require a calibration update? If yes, go to step  14. If no, go to next step.
  5. Turn ignition off. Disconnect the PCM. Measure the resistance between terminal C2-20 and C2-21. Is the resistance 966-2200 ohms? If yes, go to step  7. If no, go to next step.
  6. Test the VSS high signal and VSS low signal circuits for the following conditions:
    • An open circuit or high resistance condition
    • VSS high signal and VSS low signal circuits shorted together

    Did you find and correct a condition? If yes, go to step  14. If no, go to step  11.

  7. Measure the resistance between the terminal C2-21 and ground. Is the resistance greater than 50K ohms? If yes, go to step  10. If no, go to next step.
  8. Leave the DVOM connected between terminal C2-21 and ground. Disconnect the VSS. Measure the resistance between terminal C2-21 and ground. Is the resistance greater than 50K ohms? If yes, go to step  11. If no, go to next step.
  9. Repair the short to ground in the VSS high signal circuit. After repairs, go to step  14.
  10. Connect the DVOM between terminal C2-20 and C2-21. Measure the AC voltage with the DVOM while rotating the drive wheels by hand. Is the AC voltage equal to or greater than 0.5 volt? If yes, go to step  13. If no, go to next step.
  11. Remove the VSS. Inspect the VSS and the VSS rotor for the following conditions:
    • VSS damage.
    • VSS rotor damage.
    • Excessive air gap between the VSS rotor and the VSS.
    • Incorrect alignment between the VSS and the VSS rotor.

    Repair or replace any of the items as necessary. Did you find and correct a condition? If yes, go to step  14. If no, go to next step.

  12. Replace the VSS. After repairs, go to step  14.
  13. Replace PCM. See appropriate REMOVAL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  14. Using the scan tool, clear the DTCs. Start engine. Idle at normal operating temperature. Operate vehicle within the Conditions for Running DTC. See CONDITIONS FOR RUNNING DTC . Does the scan tool indicate that this diagnostic has run and passed? If yes, system is okay. If no, go to step  2.
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