LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Subaru >> 1997 >> Legacy Outback, Standard >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> Circuit Tests >> DTC P0122 (THV_Low): TP Sensor Circuit Low Input
April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC P0122 (THV_Low): TP Sensor Circuit Low Input

  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, system is normal. Check for poor contact in connectors and intermittent open in wiring. If displayed voltage is 0.1 volt or more, go to next step.
  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 with known good ECM and retest.
  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, check voltage while wiggling wiring and connector of ECM. If voltage changes to less than .1 volt, 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.
scientia non olet · About LEMON Manuals