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Home >> Pontiac >> 2001 >> Aztek Base, AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics >> Diagnostic Tests >> DTC P0121: Throttle Position Sensor Performance >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform powertrain diagnostic system check. See POWERTRAIN DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
  2. Using scan tool, check for DTCs. If any other DTCs are set, diagnose affected DTCs first. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no other DTCs are set, observe TP sensor angle parameter on scan tool while slowly opening throttle from closed position to Wide Open Throttle (WOT) position. If TP angle value increases steadily and evenly from zero (closed) to 98 percent (WOT), go to next step. If TP sensor angle value does not increase steadily and evenly from zero (closed) to 98 percent (WOT), go to step  4.
  3. Observe FREEZE FRAME/FAILURE RECORDS data for this DTC. Turn ignition off for 30 seconds. Operate vehicle within conditions for running this DTC or as close to FREEZE FRAME/FAILURE RECORDS data observed. See CODE ENABLE CRITERIA . If DTC fails this ignition, go to next step. If DTC does not fail this ignition, see DIAGNOSTIC AIDS .
  4. Turn ignition off. Disconnect TP sensor harness connector. Turn ignition on, with engine off. Using scan tool, observe TP sensor voltage parameter. If TP sensor voltage parameter is zero volts, go to next step. If TP sensor voltage parameter is not zero volts, go to step  6.
  5. Turn ignition off. Connect fused jumper wire between TP sensor harness connector terminals "A" (Gray wire) and "C" (Dark Blue wire). Turn ignition on, with engine off. Using scan tool, observe TP sensor voltage parameter. If TP sensor voltage parameter is 5 volts, go to step  9. If TP sensor voltage parameter is not 5 volts, go to step  7.
  6. Turn ignition off. Check for short to voltage in Dark Blue wire between TP sensor harness connector terminal "C" and PCM harness connector C2 terminal No. 66. Repair as necessary. After repairs, go to step  14. If circuit is okay, go to step  12.
  7. Turn ignition off. Check for open or high resistance in Gray wire between TP sensor harness connector terminal "A" and PCM harness connector C2 terminal No. 33. Repair as necessary. After repairs, go to step  14. If circuit is okay, go to next step.
  8. Check for open or high resistance in Dark Blue wire between TP sensor harness connector terminal "C" and PCM harness connector C2 terminal No. 66. See Figure. Repair as necessary. After repairs, go to step  14. If circuit is okay, go to step  11.
  9. Turn ignition off. Check for open or high resistance in Black wire between TP sensor harness connector terminal "B" and PCM harness connector C1 terminal No. 61. See Figure. Repair as necessary. After repairs, go to step  14. If circuit is okay, go to next step.
  10. Check for poor connection at TP sensor harness connector. Repair as necessary. After repairs, go to step  14. If connections are okay, go to step  12.
  11. Check PCM harness connector for poor connection. Repair as necessary. After repairs, go to step  14. If connections are okay, go to step  13.
  12. Replace TP sensor. After replacing sensor, go to step  14.
  13. Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  14. Turn ignition on, with engine off. Using scan tool, clear DTCs. Turn ignition off for 30 seconds. Operate vehicle within conditions for running this DTC. See CODE ENABLE CRITERIA . If DTC runs and passes, go to next step. If DTC resets, go to step  2.
  15. Using scan tool, observe the stored information and CAPTURE INFO. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no DTCs are displayed, system is okay.
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