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Home >> Oldsmobile >> 1998 >> 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 POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . Read and record FREEZE FRAME and/or FAIL RECORDS data for each DTC set. After performing OBD system check, go to next step.
  2. If DTC P0403, P1404, P1374 or P1626 is also set, diagnose affected DTC(s). If these DTCs are not set, turn ignition on, engine off. Using scan tool, read MAP value. If value is less than 65 kPa, go to next step. If value is not less than 65 kPa, 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 value is not less than 65 kPa, go to next step.
  4. Check MAP sensor signal circuit for open or short between PCM and MAP sensor. Repair as necessary. After repairs, go to step 13). If circuit is okay, 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 TP voltage is not zero volts, 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 scan tool voltage is not 5 volts, go to step 10).
  9. Check TP sensor signal circuit for short to ground. Check ground circuit for high resistance or poor connection. Repair as necessary. After repairs, go to step 13). If circuits and connections are okay, go to step 12).
  10. Check TP sensor 5-volt reference circuit for poor connection or high resistance in circuit between PCM and TP sensor. Repair as necessary. After repairs are complete, go to step 13). If connections and circuits are okay, 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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