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Home >> Oldsmobile >> 2003 >> Bravada AWD >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Self-Diagnostics - 4.2L >> Diagnostic Tests >> DTC P1120: Throttle Position Sensor 1 Circuit >> Diagnostic Procedures

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. Turn ignition on, with engine off. With scan tool, observe the TP sensor voltage with the accelerator pedal in the rest position. Does scan tool indicate voltage less than 0.27 volt or greater than 4.67 volts? If yes, go to step  5. If no, go to next step.
  3. Is DTC P1221 also set? If yes, see DTC P1221: THROTTLE POSITION SENSORS 1 & 2 CORRELATION . If no, go to next step.
  4. Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the Conditions For Running DTC or as close to the Freeze Frame/Failure Records data that you observed. See CONDITIONS FOR RUNNING DTC . Does the DTC fail this ignition cycle? If yes, go to next step. If no, problem is intermittent. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER EXT article.
  5. Turn ignition off. Disconnect the throttle body harness connector. Turn ignition on, with engine off. With scan tool, observe the TP sensor 1 voltage parameter. Does scan tool indicate voltage at zero volts? If yes, go to next step. If no, go to step  11.
  6. Connect a fused jumper wire between the TP sensor 5-volt reference circuit and the TP sensor signal circuit at the throttle body harness connector. With scan tool, observe the TP sensor 1 voltage parameter. Does scan tool indicate the TP sensor 1 voltage at 5 volts? If yes, go to next step. If no, go to step  8.
  7. With a test light connected to battery voltage, probe the TP sensor low reference circuit. Does the test light illuminate? If yes, go to step  17. If no, go to step  13.
  8. With a DVOM, measure the voltage of the TP sensor 1 5-volt reference circuit. Does the DVOM indicate voltage at 5 volts? If yes, go to step  10. If no, go to next step.
  9. Does the DVOM indicate voltage less than 5 volts on the TP sensor 1 5-volt reference circuit? If yes, go to step  14. If no, go to step  16.
  10. Test the TP sensor 1 signal circuit for an open or high resistance. Did you find and correct the condition? If yes, go to step  21. If no, go to step  12.
  11. Test the TP sensor 1 signal circuit for a short to voltage. Did you find and correct the condition? If yes, go to step  21. If no, go to step  19.
  12. Test the TP sensor 1 signal circuit for a short to ground. Did you find and correct the condition? If yes, go to step  21. If no, go to step  19.
  13. Test the TP sensor 1 low reference circuit for an open or high resistance. Did you find and correct the condition? If yes, go to step  21. If no, go to step  19.
  14. Test the TP sensor 1 5-volt reference circuit for an open or high resistance. Did you find and correct the condition? If yes, go to step  21. If no, go to next step.
  15. Test the TP sensor 1 5-volt reference circuit for a short to ground. Repair as necessary. After repairs, go to step  21. If no, go to step  19.
  16. Test the TP sensor 1 5-volt reference circuit for a short to voltage. Repair as necessary. After repairs, go to step  21.
  17. Inspect for poor connections at the throttle body harness connector. Did you find and correct the condition? If yes, go to step  21. If no, go to next step.
  18. Replace throttle body assembly. See REMOVAL & INSTALLATION - BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER EXT article. After repairs, go to step  21.
  19. Inspect for poor connections at the PCM harness connector. Did you find and correct the condition? If yes, go to step  21. If no, go to next step.
  20. Replace PCM. See REMOVAL & INSTALLATION - BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER EXT article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  21. Clear the DTCs with scan tool. Turn ignition off for 30 seconds. Start engine. Operate vehicle within the Conditions For Running DTC. See CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  22. Observe the stored information, Capture Info with scan tool. Does 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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