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Home >> Buick >> 1996 >> Century Custom >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Tests W/Codes - 2.2L >> Diagnostic Trouble Codes >> DTC P0121 - TP Sensor System Performance >> Diagnostic Procedures

Diagnostic Procedures

  1. Perform On-Board Diagnostic (OBD) System Check. After performing OBD system check, go to next step.
  2. Turn ignition on, with engine off. Observing scan tool, depress accelerator to floor, then slowly release pedal. TP sensor angle value should increase steadily to about 95 percent when pedal is depressed and decrease steadily to about 2 percent when pedal is released. If TP sensor angle value is as specified, go to next step. If TP sensor angle value is not as specified, go to step 4).
  3. Turn ignition on, with engine off. Using scan tool, review FREEZE FRAME data and note parameters. Start engine and operate vehicle within conditions required for setting this DTC, and as close to conditions recorded in FREEZE FRAME as possible. If TP sensor angle value-versus-RPM value is more than specified value in conditions for setting DTC, go to next step. If TP sensor angle value-versus-RPM value is not more than the specified value in conditions for setting DTC, go to step 12).
  4. Disconnect TP sensor connector. Observe TP sensor display on scan tool. If TP sensor voltage is less than .5 volt, go to next step. If TP sensor voltage is .5 volt or more, go to step 6).
  5. Connect a jumper wire between 5-volt reference circuit and signal circuit terminals at TP sensor harness connector. If scan tool voltage is more than 4.5 volts, go to step 7). If scan tool voltage is 4.5 volts or less, go to step 8).
  6. Check TP signal circuit for short to voltage. Repair wiring as necessary. After repair is completed, go to step 12). If circuit is okay, go to step 9).
  7. Check TP sensor ground circuit for high resistance between PCM and TP sensor. Check TP sensor ground circuit for poor connection. Repair as necessary. After repair is completed, go to step 12). If circuit is okay, go to step 10).
  8. Check TP sensor signal circuit for high resistance between PCM and TP sensor connectors. Repair as necessary. After repair is completed, go to step 12). If circuit is okay, go to next step.
  9. Disconnect and inspect TP sensor and PCM connectors. Repair connectors as necessary. After repair is completed, go to step 12). If connectors are okay, go to step 11).
  10. Replace TP sensor. After repair is completed, go to step 12).
  11. Replace PCM. Program replacement PCM using required equipment. After repair is completed, go to next step.
  12. Using scan tool, select CLEAR INFO or CLEAR DTCS function to clear DTCs. Start and warm engine to normal operating temperature. Operate vehicle within conditions required for setting this DTC. Select SPECIFIC DTC function then enter DTC P0121. If scan tool indicates TEST RAN AND PASSED, go to next step. If scan tool does not indicate TEST RAN AND PASSED, repeat step 2).
  13. If any other DTCs are set, diagnose DTCs as necessary. If no other DTCs are set, no problem is indicated at this time.
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