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Home >> Chevrolet >> 2002 >> 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 diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check, go to next step.
  2. With the throttle closed, select the TP sensor parameter on the scan tool. Is the TP sensor percentage more than 25 percent. If yes, go to step  5 . If no, go to next step.
  3. Monitor the TP sensor with the throttle closed. Is the TP sensor percentage less than 6 percent. If yes, go to step  12 . If no, go to next step.
  4. Perform the scan tool Clear DTC Information function. Place the vehicle into Check Mode, using the scan tool. Operate the vehicle within the Freeze Frame conditions as specified. Does DTC P0120 set? If yes, go to step  2 . If no, see DIAGNOSTIC AIDS  .
  5. Turn OFF the ignition. Disconnect the TP sensor electrical connector. Turn ON ignition, with engine OFF. Monitor the TP sensor on the scan tool. Is the TP sensor percentage more than 0 percent. If yes, go to step  7 . If no, go to next step.
  6. Probe the TP sensor ground circuit on the harness side, using a test light connected to battery voltage. Does the test light illuminate? If yes, go to step  8 . If no, go to step  10 .
  7. Turn OFF the ignition. Disconnect PCM harness connectors. Turn ON ignition, with engine OFF. Check for a short to voltage in the TP sensor input circuit. Repair as necessary. Was a repair necessary? If yes, go to step  21 . If no, go to step  20 .
  8. Turn ON ignition, with engine OFF. Use a Digital Multimeter (DMM) to measure voltage at reference voltage circuit on harness side. Does voltage equal 5.0 volts? If yes, go to next step. If no, go to step  11 .
  9. Check for a faulty electrical connection at the TP sensor and the PCM. Replace the terminals if necessary. Was a repair necessary? If yes, go to step  21 . If no, go to step  18 .
  10. Turn OFF the ignition. Disconnect PCM harness connectors. Check for an open in the TP sensor ground circuit. Repair as necessary. Was a repair necessary? If yes, go to step  21 . If no, go to step  20 .
  11. Turn OFF the ignition. Disconnect the PCM electrical connector at the PCM. Check the reference voltage circuit for an open or a short. Repair as necessary. Was a repair necessary? If yes, go to step  21 . If no, go to step  20 .
  12. Disconnect the TP sensor electrical connector. Jump the 5-volt reference circuit and the TP sensor input circuit together at the TP sensor harness connector. Select the TP sensor on the scan tool. Is the TP sensor percentage more than 90 percent? If yes, go to step  18 . If no, go to next step.
  13. Connect a test light between battery voltage and the TP sensor input circuit at the TP sensor harness connector. Monitor the TP sensor on the scan tool. Is the TP sensor percentage more than 90 percent? If yes, go to next step. If no, go to step  16 .
  14. Turn OFF the ignition. Disconnect the PCM electrical connector at the PCM. Check the 5-volt reference circuit for an open or a short. Repair as necessary. Was a repair necessary? If yes, go to step  21 . If no, go to next step.
  15. Check the 5-volt reference circuit for a faulty electrical connection at the TP sensor and the PCM. Repair as necessary. Was a repair necessary? If yes, go to step  21 . If no, go to step  20 .
  16. Turn OFF the ignition. Disconnect PCM harness connectors. Check TP input circuit for an open or a short to ground. Ensure that the input circuit is not shorted to the sensor ground circuit. Repair the circuit as necessary. Was a repair necessary? If yes, go to step  21 . If no, go to next step.
  17. Check the TP sensor input circuit for a faulty connection at the PCM. Repair as necessary. Was a repair necessary? If yes, go to step  21 . If no, go to step  20 .
  18. Check the TP sensor terminals and the terminal connections. Repair as necessary. Was a repair necessary? If yes, go to step  21 . If no, go to next step.
  19. Replace TP sensor. After repairs, go to step  21 .
  20. Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  21. Use the scan tool in order to clear the DTCs. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC  . Does the DTC run and pass? If yes, go to next step. If no, go to step  2 .
  22. With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, go to DIAGNOSTIC TROUBLE CODE DEFINITIONS  . If no, system is okay.
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