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Home >> Chevrolet >> 2000 >> Impala LS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System - Self-Diagnostics - 3.8L >> Diagnostic Tests >> DTC P0121: TP Sensor Performance >> Diagnostic Procedures
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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. Using scan tool, monitor TP angle reading while slowly opening throttle. If TP angle reading increases steadily from zero percent to 100 percent, see DIAGNOSTIC AIDS . If operation is not as specified, go to next step.
  3. Turn ignition off. Disconnect TP sensor harness connector. Turn ignition on. Using scan tool, monitor TP sensor voltage. If voltage is near zero volts, go to next step. If voltage is not near zero volts, go to step  5.
  4. Turn ignition off. Using a fused jumper wire, jumper 5-volt reference circuit and signal circuit together at TP sensor harness connector. Turn ignition on. Using scan tool, monitor TP sensor voltage. If voltage is 5 volts, go to step  8. If voltage is not 5 volts, go to step  6.
  5. Check TP sensor signal circuit for a 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 for poor connections at PCM. Repair as necessary. After repairs, go to step  12. If connections are 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 replacing PCM, go to next step.
  12. Turn ignition on, engine off. Using scan tool, read and record FAILURE RECORDS data, and clear DTCs. Operate vehicle within conditions noted in FAILURE RECORDS data. Using scan tool, select 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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