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Diagnostic Procedures

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  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. Install a scan tool. Raise the drive wheels. Start the engine. Disable the traction control system, if equipped. Shift the transmission into third gear. Slowly release the clutch. With the drive wheels rotating, does the vehicle speed increase with drive wheel speed increase? If yes, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM. If no, go to next step.
  3. Turn OFF the ignition. Shift the transmission into Neutral. Back probe the VSS buffer module ignition feed circuit with a test light connected to ground. Is the test light ON? If yes, go to next step. If no, go to step  7 .
  4. Back probe the VSS buffer module ignition feed circuit to the ground circuit with a test light. Is the test light ON? If yes, go to next step. If no, go to step  8 .
  5. Back probe the VSS buffer module at the VSS input circuit (C7) to the other VSS input circuit (C12) with a Digital Multimeter (DMM) on the AC scale. Place the transmission in any drive range with the drive wheels rotating. Does the voltage increase on the DMM with drive wheel increase? If yes, go to next step. If no, go to step  9 .
  6. Does the scan tool display a trans output speed (MPH) increase with drive wheel increase? If yes, go to step  12 . If no, go to step  11 .
  7. Repair the open in the ignition feed circuit. After repairs, go to step  17 .
  8. Repair the open in the ground circuit. After repairs, go to step  17 .
  9. Test the complete VSS input circuit for an open or short to ground. Was a repair performed? If yes, go to step  17 . If no, go to next step.
  10. Test the VSS connector for an open or high resistance condition. If a condition is found, repair the condition as necessary. Was a condition found? If yes, go to step  17 . If no, go to step  14 .
  11. Back probe the VSS buffer module at the VSS output circuit (C15) with a DMM connected to ground. Place the transmission in any drive range with the drive wheels rotating. Is there voltage present? If yes, go to next step. If no, go to step  15 .
  12. Test the VSS output circuit for an open or short to ground. Was a repair performed? If yes, go to step  17 . If no, go to next step.
  13. Test the VSS output circuit connections at the PCM for an open or high resistance condition. Was a repair performed? If yes, go to step  17 . If no, go to step  16 .
  14. Replace the vehicle speed sensor. After repairs, go to step  17 .
  15. Replace the VSS Buffer module. After repairs, go to step  17 .
  16. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  17. Using the scan tool, clear the DTCs. Start the engine and idle at normal operating temperature. Select DTC, Specific, then enter the DTC number which was set. Operate the vehicle within the Conditions for Setting DTC, until the scan tool indicates the diagnostic Ran. Does the scan tool indicate the diagnostic Passed? If yes, system is okay. If no, go to step  2 .
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