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Home >> Oldsmobile >> 1997 >> Regency >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control Systems Tests W/Codes >> Diagnostic Trouble Codes >> DTC P0121 - TP Sensor System Performance >> Diagnostic Procedures
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Diagnostic Procedures

  1. Perform ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK. See the BASIC TESTING - 3.8L article. Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. Go to next step.
  2. If DTC P1635  is also set, go to that DTC. If not, turn ignition on, engine off. Using scan tool, read MAP value. If value is less than 65 kPa, go to next step. If not, go to step 6).
  3. Disconnect MAP sensor harness connector. Connect a test light between MAP sensor harness connector 5-volt reference and signal circuits. Using scan tool, read MAP value. If value is less than 65 kPa, go to step 5). If not, go to next step.
  4. Check MAP sensor signal circuit for open or short between PCM and MAP sensor. If problem is found, repair as necessary. After repairs, go to step 13). If no problem is found, go to step 12).
  5. Replace MAP sensor. After replacing sensor, go to step 13).
  6. Observe scan tool TP ANGLE value while moving throttle from closed to wide open throttle. If value increases steadily and evenly from closed to open throttle, see DIAGNOSTIC AIDS. If value does not increase as specified, go to next step.
  7. Disconnect TP sensor harness connector. If TP voltage is zero volts, go to next step. If not, go to step 9).
  8. Connect a test light between TP sensor harness connector 5-volt reference and signal circuits. Using scan tool, read TP sensor voltage. If scan tool voltage is 5 volts, go to step 11). If voltage is not as specified, go to step 10).
  9. Check TP sensor signal circuit for short to ground, ground circuit for high resistance and poor connection. Repair as necessary and go to step 13). If no problem is found, go to step 12).
  10. Check TP sensor 5-volt reference circuit for poor connection or high resistance between PCM and TP sensor. Repair as necessary and go to step 13). If no problem is found, go to step 12).
  11. Replace TP sensor. After replacing sensor, go to step 13).
  12. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  13. Turn ignition on, engine off. Using scan tool, read and record FAIL RECORDS DATA, and clear DTCs. Operate vehicle within conditions noted in FAIL RECORDS data. Using scan tool, select SPECIFIC DTC INFO for DTC P0117 . If scan tool displays DTC P0117 FAILED THIS IGN, return to step 2). If scan tool does not display DTC P0117 FAILED THIS IGN, repair is complete.
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