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Home >> Pontiac >> 2002 >> Aztek FWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics >> Diagnostic Tests >> DTC P0121: TP Sensor Performance >> Diagnostic Procedures
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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. NOTE: If any other DTCs are set, diagnose those DTCs first.
  2. Turn ON the ignition, with the engine OFF. Observe the TP sensor angle parameter on the scan tool while slowly opening the throttle to WOT. The closed throttle value is 0%. The WOT value is more than 98%. Does the TP angle increase steadily and evenly from the closed throttle value to more than the WOT value? If yes, go to next step. If no, go to step  4.
  3. Observe the Freeze Frame/Failure Records for this DTC. Turn OFF the ignition for 30 seconds. Operate the vehicle within the Conditions for Running DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Does the DTC fail this ignition cycle? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  4. Turn OFF the ignition. Disconnect the TP sensor harness connector. Turn ON the ignition, with the engine OFF. Observe the TP sensor voltage parameter with a scan tool. Does the voltage equal 0 V? If yes, go to next step. If no, go to step  6.
  5. Turn OFF the ignition. Connect a fused jumper between the 5-volt reference circuit and the signal circuit at the TP sensor harness connector. Turn ON the ignition, with the engine OFF. Observe the TP sensor voltage parameter with a scan tool. Does the voltage equal 5 V? If yes, go to step  9. If no, go to step  7.
  6. Test the TP sensor signal circuit for a short to voltage with a Digital Multimeter (DMM). Did you find and correct the condition? If yes, go to step  15. If no, go to step  12.
  7. Test the 5-volt reference circuit of the TP sensor for an open or high resistance with a DMM. Did you find and correct the condition? If yes, go to step  15. If no, go to next step.
  8. Test the TP sensor signal circuit for an open or high resistance. Did you find and correct the condition? If yes, go to step  15. If no, go to step  12.
  9. Test the TP sensor low reference circuit for an open and for high resistance. Did you find and correct the condition? If yes, go to step  15. If no, go to next step.
  10. Test the TP sensor 5-volt reference circuit for high resistance. Did you find and correct the condition? If yes, go to step  15. If no, go to next step.
  11. Inspect for a faulty connection at the TP sensor harness connector. Did you find and correct the condition? If yes, go to step  15. If no, go to step  13.
  12. Inspect for a faulty connection at the PCM harness connector. Did you find and correct the condition? If yes, go to step  15. If no, go to step  14.
  13. Replace the TP sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. 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. Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  16. Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
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