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Home >> Chevrolet >> 2000 >> Prizm Base, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls Self-Diagnostics - 1.8L >> Diagnostic Tests >> DTC P0120: TP Sensor Circuit >> Diagnostic Procedures

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. Connect scan tool to DLC. Turn ignition on, with engine off. With throttle closed, monitor TP sensor parameter. If TP sensor value is greater than 25 percent, go to step  5 . If TP sensor value is 25 percent or less, go to next step.
  3. Observe TP sensor with throttle closed. If TP sensor value is less than 6 percent, go to step  12 . If TP sensor value is 6 percent or greater, go to next step.
  4. Turn ignition on, with engine off. Using scan tool, clear DTC information. Using scan tool, place vehicle into check mode. Operate vehicle within freeze frame conditions. If DTC resets, go to step  2 . If DTC does not reset, see DIAGNOSTIC AIDS  .
  5. Turn ignition off. Disconnect TP sensor harness connector. Turn ignition on, with engine off. Using scan tool, observe TP sensor parameter. If TP sensor value is greater than zero percent, go to step  7 . If TP sensor value is zero percent, go to next step.
  6. Using test light connected to battery voltage, probe TP sensor connector ground circuit. See WIRING DIAGRAMS article. If test light illuminates, go to step  8 . If test light does not illuminate, go to step  10 .
  7. Turn ignition off. Disconnect PCM harness connector. Turn ignition on, with engine off. Check for a short to voltage in PCM harness connector TP sensor input circuit. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step  21 . If circuit is okay, go to step  20 .
  8. Turn ignition on, with engine off. Using DVOM, check voltage at TP sensor connector (harness side) reference voltage circuit. See WIRING DIAGRAMS article. If voltage reading is 5 volts, go to next step. If voltage reading is not 5 volts, go to step  11 .
  9. Check for poor connections at PCM and TP sensor. Repair as necessary. After repairs, go to step  21 . If connections are okay, go to step  18 .
  10. Turn ignition off. Disconnect PCM harness connector. Check for open in TP sensor ground circuit at PCM harness connector. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step  21 . If circuit is okay, go to step  20 .
  11. Turn ignition off. Disconnect PCM harness connector. Check for open or short in TP sensor reference voltage circuit at PCM harness connector. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step  21 . If circuit is okay, go to step  20 .
  12. Disconnect TP sensor harness connector. Using a fused jumper wire, connect TP sensor harness connector reference voltage and input circuits together. See WIRING DIAGRAMS article. Using scan tool, monitor TP sensor parameter. If TP sensor value is greater than 90 percent, go to step  18 . If TP sensor value is 90 percent or less, go to next step.
  13. Connect a test light between battery voltage and TP sensor harness connector input circuit. See WIRING DIAGRAMS article. Using scan tool, monitor TP sensor parameter. If TP sensor value is greater than 90 percent, go to next step. If TP sensor value is 90 percent or less, go to step  16 .
  14. Turn ignition off. Disconnect PCM harness connector. Check for open or short in TP sensor reference voltage circuit at PCM harness connector. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step  21 . If circuit is okay, go to next step.
  15. Check for poor connections at PCM and TP sensor. Repair as necessary. After repairs, go to step  21 . If connections are okay, go to step  20 .
  16. Turn ignition off. Disconnect PCM harness connector. Check for open or short to ground in TP sensor input circuit at PCM harness connector. See WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step  21 . If circuit is okay, go to next step.
  17. Check for poor connections at PCM. Repair as necessary. After repairs, go to step  21 . If connections are okay, go to step  20 .
  18. Check for poor connections at TP sensor. Repair as necessary. After repairs, go to step  21 . If connections are okay, go to next step.
  19. Replace TP sensor. After repairs, go to step  21 .
  20. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  21. After repairs, using scan tool, clear DTC information. Road test vehicle within freeze frame conditions that set DTC. Check for DTCs. If no DTCs are stored, repair is complete. If any DTCs are stored, diagnose affected DTC(s).
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