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DTC P0120 (THV): Throttle Position (TP) Sensor Circuit Malfunction

  1. Turn ignition off. Connect SSM. Start engine. Set SSM function mode to F07 to check TP sensor output signal. If displayed voltage is less than 0.1 volt, go to next step. If displayed voltage is 0.1 volt or more, go to step 7).
  2. Turn ignition off. Ensure throttle valve is fully closed. Turn ignition on. Using DVOM connected to chassis ground, backprobe ECM connector terminal No. 21. See appropriate wiring diagram in WIRING DIAGRAMS article. If voltage is 4.5 volts or more, go to next step. If voltage changes to more than 4.5 volts while wiggling wiring and connector, repair poor contact in wiring or ECM connector. If voltage remains less than 4.5 volts, replace ECM.
  3. Backprobe ECM connector terminal No. 6. If voltage is 0.1 volt or less, go to next step. If voltage is more than 0.1 volt while wiggling wiring and connector of ECM, repair poor contact in wiring or ECM connector. If voltage remains more than 0.1 volt, go to next step.
  4. Turn ignition off. Disconnect TP sensor connector. Turn ignition on. Check voltage between TP sensor connector terminal No. 3 and chassis ground. If voltage is 4.5 volts or more, go to next step. If voltage is less than 4.5 volts, check for open circuit in wiring between TP sensor and ECM connector. Check for poor contact in ECM and TP sensor connectors.
  5. Turn ignition off. Disconnect ECM connector. Check resistance between ECM connector terminal No. 6 and TP sensor connector terminal No. 2. If resistance is less than one ohm, go to next step. If resistance is one ohm or more, check for open in wiring between TP sensor and ECM connector, or check for poor terminal contact in ECM and TP sensor connectors.
  6. Check resistance between TP sensor connector terminal No. 2 and chassis ground. If resistance is less than 10 ohms, check for short in wiring between TP sensor and ECM connector. If resistance is 10 ohms or more, check for poor terminal contact in TP sensor or connector. If contact is okay, replace TP sensor.
  7. If value is more than 4.9 volts, go to next step. If value is 4.9 volts or less, check for poor terminal contact in ECM and TP sensor connectors. See appropriate wiring diagram in WIRING DIAGRAMS article. Check for poor terminal contact in wiring harness coupling connector.
  8. Turn ignition off. Disconnect TP sensor connector. Check resistance between TP sensor connector terminal No. 1 and chassis ground. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or more, check for open in wiring between ECM and TP sensor connector, and for poor terminal contact.
  9. Turn ignition on. Check voltage between TP sensor connector terminal No. 2 and chassis ground. If voltage reading is more than 4.9 volts, check for short to voltage in wiring between ECM and TP sensor connector. If voltage reading is 4.9 volts, replace TP sensor.
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