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Home >> GMC >> 2002 >> Jimmy 2D Utility, Part Time, Automatic >> Repair and Diagnosis >> External Pages >> Different car >> Section 387 (Engine Controls Self-Diagnostics) >> Diagnostic Tests >> DTC P0502: Vehicle Speed Sensor Low Output >> Diagnostic Procedures
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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. NOTE: Before clearing the DTC, use the scan tool in order to record the Freeze Frame and Failure Records. Using the Clear Info function erases the Freeze Frame and 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 and support the rear axle assembly. Start the engine. Place the transmission in any drive range. With the drive wheels rotating, does the scan tool Transmission OSS increase with the drive wheel speed? If yes, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM. If no, go to next step.
  3. Turn ignition OFF. Disconnect the engine wiring harness from the VSS. Measure the resistance of the VSS assembly. Does the resistance measure 976-2354 ohms? If yes, go to next step. If no, go to step  13.
  4. Measure the resistance between VSS connector terminal "B" and ground. Does the resistance measure greater than 50 k/ohms? If yes, go to next step. If no, go to step  13.
  5. Place the transmission in Neutral. Select AC volts on the DVOM. Hold one rear wheel from turning. Rotate the other wheel by hand. Measure the AC voltage from terminal "A" and "B" of the VSS assembly. Does the voltage measure greater than 0.3 V AC? If yes, go to next step. If no, go to step  13.
  6. Reconnect the engine wiring harness to the VSS assembly. Disconnect PCM connector C2. Measure the resistance between PCM connector C2 terminals No. 20 and No. 21. Does the resistance measure 976-2354 ohms? If yes, go to next step. If no, go to step  8.
  7. Measure the resistance between PCM connector C2 terminal No. 21 and ground. Does the resistance measure greater than 50 k/ohms? If yes, go to step  9. If no, go to step  10.
  8. Does the resistance measure greater than 2354 ohms? If yes, go to step  11. If no, go to step  12.
  9. Reconnect the PCM connector C2. Disconnect the engine wiring harness from the VSS assembly. Turn ignition ON, with engine OFF. Test the high circuit (CKT 400) of the VSS assembly for a short to power. Test the low circuit (CKT 401) of the VSS assembly for a short to power. Did you find and correct the condition? If yes, go to step  15. If no, go to step  14.
  10. Test the high circuit (CKT 400) of the VSS assembly for a short to ground. Test the low circuit (CKT 401) of the VSS assembly for a short to ground. Repair as necessary. Did you find and correct the condition? If yes, go to step  15.
  11. Test the high circuit (CKT 400) of the VSS assembly for an open. Test the low circuit (CKT 401) of the VSS assembly for an open. Repair as necessary. Did you find and correct the condition? If yes, go to step  15.
  12. Test the high circuit (CKT 400) and the ground circuit (CKT 401) of the VSS assembly for a short together. Did you find and correct the condition? If yes, go to step  15.
  13. Replace VSS assembly. See VEHICLE SPEED SENSOR under SENSORS in REMOVAL & INSTALLATION - CORVETTE article. Did you complete the replacement? If yes, go to step  15.
  14. 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.
  15. Perform the following procedure in order to verify the repair:
    1. Select DTC.
    2. Select Clear Info.
    3. Operate the vehicle, so that the transmission output speed is greater than 500 RPM for 3 seconds.
    4. Select Specific DTC.
    5. Enter DTC P0502.

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

  16. 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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