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DTC P0122: Throttle Position (TP) Sensor Circuit Low Input

  1. Turn ignition off. Connect scan tool. Start engine. Observe 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, system has returned to normal. Check for poor connection between ECM and TP sensor connectors.
  2. Ensure throttle valve is fully closed. Using DVOM connected to ground, backprobe ECM connector B136 (30-pin connector) terminal No. 15. See Figure. If voltage is more than 4.5 volts, go to step  4. If voltage is 4.5 volts or less, go to next step.
  3. Observe DVOM while wiggling ECM connector. If voltage change is more than 4.5 volts while wiggling connector, check for poor contact at ECM connector. If voltage does not change more than 4.5 volts, replace ECM.
  4. Backprobe ECM connector B136 (30-pin connector) terminal No. 17. If voltage is less than .1 volt, go to step  6. If voltage is .1 volt or more, go to next step.
  5. Observe DVOM while wiggling ECM connector. If voltage changes more than .1 volt while wiggling connector, repair poor contact at ECM connector. If voltage does not change more than .1 volt, go to next step
  6. Turn ignition off. Disconnect TP sensor connector. Turn ignition on. Measure voltage between ground and TP sensor connector terminal No. 1 on 2.2L and Legacy 2.5L M/T or No. 4 on all except 2.2L and Legacy 2.5L M/T. See Figure and Figure . If voltage is 4.5 volts or more, go to next step. If voltage is less than 4.5 volts, repair open in wiring or poor connection between ECM and TP sensor connectors. See appropriate wiring diagram in WIRING DIAGRAMS article.
  7. Measure resistance between ECM connector B136 (30-pin connector) terminal No. 17 and TP sensor connector terminal No. 3. If resistance is less than one ohm, go to next step. If resistance is one ohm or more, repair open in wiring or poor connection between ECM and TP sensor connectors.
  8. Measure resistance between ground and TP sensor connector terminal No. 3. If resistance is less than 10 ohms, repair short in wiring between ECM and TP sensor connectors. If resistance is 10 ohms or more, go to next step.
  9. Check for poor terminal contact in TP sensor connector. Repair TP sensor connector as necessary. If connection is okay, replace TP sensor.
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