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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 P0121: TP Sensor System Performance >> Diagnostic Procedures
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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. Turn ON ignition, with engine OFF. Install a scan tool. Select the TP angle parameter on the scan tool. Monitor the scan tool while depressing the accelerator pedal, repeat the procedure several times. Does the TP angle value increase steadily when the accelerator pedal is depressed and decrease steadily when the pedal is released, within range of 8-80 percent? If yes, go to next step. If no, go to step  4 .
  3. Perform the scan tool Clear DTC Information function. Place the vehicle into Check Mode operation using the scan tool. Operate the vehicle within the Freeze Frame conditions as specified. Does DTC P0121 set? If yes, go to next step. If no, see DIAGNOSTIC AIDS  .
  4. Connect Digital Multimeter (DMM) between the TP sensor reference voltage circuit on the harness side and ground. Turn ON the ignition, leaving the engine OFF. Is the TP sensor voltage at 5 volts? If yes, go to next step. If no, go to step  6 .
  5. Connect a test light between the reference voltage circuit and ground. Turn ON the ignition, leaving the engine OFF. Does the test light illuminate at least dimly? If yes, go to step  7 . If no, go to step  9 .
  6. Inspect for short to voltage in the TP sensor input circuit or for proper mating of the TP sensor electrical connectors. Repair as necessary. After repairs, go to step  12 .
  7. Connect a test light between the TP sensor input circuit and the TP sensor reference voltage circuit at the harness connector. Monitor the TP angle on the scan tool. Is the TP sensor percentage more than 90 percent? If yes, go to step  10 . If no, go to next step.
  8. Check for the following conditions: High resistance in TP sensor ground circuit between sensor and S206, or high resistance in TP sensor input circuit between TP sensor and PCM Repair as necessary. Was a repair necessary? If yes, go to step  12 . If no, go to step  11 .
  9. Locate and repair the high resistance in the reference voltage circuit of the TP sensor. After repairs, go to step  12 .
  10. Replace the TP sensor. After replacing sensor, go to step  12 .
  11. Replace PCM. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  12. 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 .
  13. 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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