LEMON Manuals: Even more car manuals for everyone
Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 108 (Engine Controls Self-Diagnostics - 5.7L Corvette) >> Diagnostic Tests >> DTC P0502: Vehicle Speed Sensor Low Output >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page is about a different car, the 2002 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 ON the ignition, with the 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 OFF the ignition. Disconnect the engine wiring harness from the VSS assembly. Using the Digital Multimeter (DMM) and the J 35616-A GM Terminal Test Kit, 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 from terminal "B" of the VSS assembly to 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 DMM. 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 the PCM connector C2. Measure the resistance between PCM connector terminals C2-20 and C2-21. Does the resistance measure 976-2354 ohms? If yes, go to next step. If no, go to step  8.
  7. Measure the resistance from terminal C2-21 to 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 ON the ignition, with the 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. After repairs, 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. After repairs, 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. After repairs, go to step  15.
  13. Replace the VSS assembly. After repairs, go to step  15.
  14. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  15. Perform the following procedure in order to verify the repair:
    • Select DTC.
    • Select Clear Info.
    • Operate the vehicle, so that the transmission output speed is greater than 250 RPM for 2 seconds.
    • Select Specific DTC.
    • Enter DTC P0502.

    Has the test run and passed? If yes, system is okay. If no, go to step  1.

scientia non olet · About LEMON Manuals