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HOMESERVICE MANUALSOLDSMOBILE1998ACHIEVA 3.1 M, 4T40E/MN4REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 1 (ENGINE CONTROLS - TESTS W/CODES - 2.4L)DIAGNOSTIC TROUBLE CODESDTC P0121 - TP SENSOR SYSTEM PERFORMANCEDIAGNOSTIC PROCEDURES
1998 Oldsmobile Achieva 3.1 M, 4T40E/MN4

Diagnostic Procedures

1998 Oldsmobile Achieva 3.1 M, 4T40E/MN4SECTION Diagnostic Procedures
WARNING: This page is about a different variant/trim than selected.
  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  , then 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 98 percent when pedal is depressed and decrease steadily to about one 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. If scan tool displays a TP voltage at less than .8 volt when throttle is fully closed, go to next step. If TP voltage is not less than .8 volt when throttle is fully closed, go to step 5).
  4. 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 greater than specified value in conditions for setting DTC, go to next step. If TP sensor angle value-versus-RPM value is not greater than the specified value in conditions for setting DTC, go to step 12).
  5. 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 greater, go to step 7).
  6. Using a test light connected to ground, probe TP sensor battery circuit at harness connector. Connect DVOM between chassis ground and harness connector ground circuit. If DVOM reads greater than .5 volt, go to step 8). If DVOM does not read greater than .5 volt, go to step 9).
  7. Check TP signal circuit for short to voltage. Repair as necessary. After repairs, go to step 16). If circuit is okay, go to step 15).
  8. Check TP sensor ground circuit for high resistance between PCM and TP sensor connectors. Check TP sensor ground circuit for poor connection. Repair as necessary. After repairs are complete, go to step 16). If circuit is okay, go to step 14).
  9. Using DVOM connected to ground, probe 5-volt reference circuit at TP sensor connector. If DVOM reads about 5 volts, go to step 13). If DVOM does not read about 5 volts, go to next step.
  10. Disconnect EGR valve, MAP, A/C and fuel pressure sensor harness connectors. Probe 5-volt reference circuit to TP sensor harness connector. If DVOM reads about 5 volts, go to next step. If DVOM does not read about 5 volts, go to step 12).
  11. Leaving DVOM connected to TP sensor 5-volt reference circuit, reconnect each disconnected component one at a time until voltage reading displays other than 5 volts. Replace component that caused voltage reading to be other than 5 volts. After replacing component, go to step 16).
  12. Check for short to voltage in TP sensor 5-volt reference circuit. Repair as necessary. After repairs are complete, go to step 16). If circuit is okay, go to step 15).
  13. Replace TP sensor. After replacing sensor, go to step 16).
  14. Check PCM harness connector for poor connection or resistance. Repair as necessary. After repairs, go to step 16). If connection is okay, go to next step.
  15. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  16. 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).
  17. 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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Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.