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Diagnostic Procedures

WARNING: This page is about a different car, the 2003 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.
  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. CAUTION: 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 a scan tool. Turn ignition ON, with engine OFF. Record the DTC Freeze Frame and Failure Records. Clear the DTC. Raise the drive wheels. Start the engine. Allow the engine to idle in gear. Does the scan tool display vehicle speed above 0 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 note the parameters. Start the engine. Operate the vehicle within the Freeze Frame conditions and Conditions for Running DTC. Does the scan tool display vehicle speed above 0 MPH? If yes, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM. If no, go to next step.
  4. Turn ignition OFF. Disconnect PCM. Measure the resistance between PCM connector C2 terminals No. 20 and No. 21. Is the resistance 966-2200 ohms? If yes, go to step  6. If no, go to next step.
  5. Test the VSS high signal circuit and the VSS low signal circuit for the following conditions:
    • An open circuit or high resistance condition.
    • VSS high signal circuit and VSS low signal circuit shorted together.

    Did you find and correct a condition? If yes, go to step  13. If no, go to step  10.

  6. Measure the resistance between PCM connector C2 terminal No. 21 and ground. Is the resistance greater than 50 k/ohms? If yes, go to step  9. If no, go to next step.
  7. Leave the DVOM connected between PCM connector C2 terminal No. 21 and ground. Disconnect VSS. Measure the resistance between PCM connector C2 terminal No. 21 and ground. Is the resistance greater than 50 k/ohms? If yes, go to step  10. If no, go to next step.
  8. Repair the short to ground in the VSS high signal circuit. Did you complete the repair? If yes, go to step  13.
  9. Reconnect the DVOM between PCM connector C2 terminals No. 20 and No. 21. Measure the AC voltage while rotating the drive wheels by hand. Is the AC voltage equal to or greater than 0.5 V? If yes, go to step  12. If no, go to next step.
  10. Remove the VSS. See VEHICLE SPEED SENSOR under SENSORS in REMOVAL & INSTALLATION - CORVETTE article. 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 above items as necessary. Did you find and correct a condition? If yes, go to step  13. If no, go to next step.

  11. Replace VSS. See VEHICLE SPEED SENSOR under SENSORS in REMOVAL & INSTALLATION - CORVETTE article. Did you complete the repair? If yes, go to step  13.
  12. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION - CORVETTE article. Did you complete the replacement? If yes, go to next step.
  13. Perform the following procedure in order to verify the repair:
    1. Select DTC.
    2. Select Clear Info.
    3. Operate the vehicle in order to achieve a vehicle speed of greater than 2 MPH for 2 seconds.
    4. Select Specific DTC.
    5. Enter DTC P0500.

    Has the test run and passed? If yes, go to next step. If no, go to step  2.

  14. Observe the stored information, Capture Info and DTC with a scan tool. Are there any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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