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Home >> Subaru >> 2001 >> Forester Base >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Self-Diagnostics - 2.2L & 2.5L >> Diagnostic Tests >> DTC P0122: Throttle Position (TP) Sensor Circuit Low Input

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

  1. Perform basic diagnostic procedure. See BASIC DIAGNOSTIC PROCEDURE . Start engine. Using scan tool, observe TP sensor signal. If voltage is less than 0.1 volt, go to next step. If voltage is not less than 0.1 volt, system has returned to normal. Check for poor terminal contact in connectors between ECM and TP sensor.
  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 not more than 4.5 volts, go to next step.
  3. Observe DVOM while wiggling harness and ECM connector. If voltage changes more than 4.5 volts while wiggling harness and ECM connector, check for poor terminal contact at ECM connector. If voltage does not change more than 4.5 volts while wiggling harness and ECM connector, contact authorized Subaru dealership because probable cause is deterioration of multiple parts.
  4. Using DVOM connected to ground, backprobe ECM connector B136 (30-pin connector) terminal No. 17. If voltage is less than 0.1 volt, go to step  6. If voltage is not less than 0.1 volt, go to next step.
  5. Observe DVOM while wiggling harness and ECM connector. If voltage changes more than 0.1 volt while wiggling harness and ECM connector, repair poor terminal contact at ECM connector. If voltage does not change more than 0.1 volt while wiggling harness and ECM connector, go to next step.
  6. Turn ignition off. Disconnect TP sensor connector. Turn ignition on. Using a DVOM connected to ground, measure voltage at TP sensor connector terminal No. 4 (terminal No. 1 on Impreza 2.2L, Legacy and Outback 2.5L M/T and Outback Sport). See Figure and Figure . If voltage is more than 4.5 volts, go to next step. If voltage is not more than 4.5 volts, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and TP sensor. See WIRING DIAGRAMS article.
  7. Turn ignition off. 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 not less than one ohm, locate and repair open circuit in wiring and check for poor terminal contact in connectors between ECM and TP sensor.
  8. Measure resistance between ground and TP sensor connector terminal No. 3. If resistance is less than 10 ohms, locate and repair short to ground in wiring between ECM and TP sensor. If resistance is not less than 10 ohms, go to next step.
  9. Check for poor terminal contact in TP sensor connector. Repair TP sensor connector as necessary. If connector is okay, replace TP sensor. Clear memory and perform verification procedure. See CLEARING DIAGNOSTIC TROUBLE CODES  and VERIFICATION PROCEDURE  .
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