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Home >> Buick >> 2000 >> Century Custom >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics - 3.1L & 3.4L >> Diagnostic Tests >> DTC P0121: TP Sensor Performance >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
  2. Turn ignition on, with engine off. Using scan tool, monitor TP sensor angle reading while slowly opening throttle. If TP sensor value increase steadily and evenly from closed throttle value to wide open throttle (0-100 percent), see DIAGNOSTIC AIDS . If TP sensor value does not increase steadily and evenly from closed throttle value to wide open throttle (0-100 percent), go to next step.
  3. Turn ignition off. Disconnect TP sensor harness connector. Turn ignition on, with engine off. Using scan tool, observe TP voltage parameter. If scan tool reading is about zero volts, go to next step. If scan tool reading is not about zero volts, go to step  5.
  4. Turn ignition off. Connect a fused jumper wire between TP sensor harness connector 5-volt reference circuit and signal circuit. If scan tool reading is 5 volts, go to step  8. If scan tool reading is not 5 volts, go to step  6.
  5. Check TP sensor signal circuit for short to voltage. Repair as necessary. After repairs, go to step  12. If circuit is okay, go to step  11.
  6. Check TP sensor 5-volt reference circuit for high resistance or poor connection at PCM. Repair as necessary. After repairs, go to step  12. If circuit is okay, go to next step.
  7. Check TP sensor signal circuit for high resistance or poor connection at PCM. Repair as necessary. After repairs, go to step  12. If circuit is okay, go to step  11.
  8. Check TP sensor ground circuit for high resistance or poor connection at PCM. Repair as necessary. After repairs, go to step  12. If circuit is okay, go to next step.
  9. Check TP sensor harness connector for poor connection. Repair as necessary. After repairs, go to step  12. If connector is okay, go to next step.
  10. Replace TP sensor. After replacing sensor, go to step  12.
  11. Replace PCM. Program replacement PCM using required equipment. After repairs, go to next step.
  12. Using scan tool, clear DTCs. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle as close to conditions recorded in FREEZE FRAME as possible. Monitor SPECIFIC DTC info for this DTC. If scan tool indicates that this DTC FAILED THIS IGN, go to step  2. If scan tool does not indicate that this DTC FAILED THIS IGN, system is okay.
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