DTC P0122: Throttle/Pedal Position Sensor/Switch "A" Circuit Low: Notes

DTC detecting condition: 

Immediately at fault recognition

Trouble symptom: 

• Improper idling
• Engine stall
• Poor driving performance

Wiring diagram: 

Engine Electrical System Ref. to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC  .
   1. Turn the ignition switch to ON.
   2. Using the Subaru Select Monitor or a general scan tool, read the DTC of [Engine]. Ref. to COMMON (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC P0122 displayed? (Current code)

   Yes:  Go to  2.

   No:  Even if DTC is detected, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

2. CHECK FOR POOR CONTACT  .
   1. Turn the ignition switch to OFF.
   2. Check for poor contact of ECM and electronic throttle control connector.

   Is there poor contact in ECM or electronic throttle control connector?

   Yes:  Repair the poor contact of ECM or electronic throttle control connector.

   No:  Go to  3.

3. CHECK HARNESS BETWEEN ECM AND ELECTRONIC THROTTLE CONTROL CONNECTOR (OPEN)  .
   1. Disconnect the connector from ECM.
   2. Disconnect the connectors from electronic throttle control.
   3. Measure the resistance of harness between ECM connector and electronic throttle control connector.

      Connector & terminal 

      (E158) No. 29 - (E57) No. 6:

      (E158) No. 27 - (E57) No. 5:

   Is the resistance less than 1 Ω?

   Yes:  Go to  4.

   No:  Repair the open circuit of harness between ECM connector and electronic throttle control connector.

4. CHECK HARNESS BETWEEN ECM AND ELECTRONIC THROTTLE CONTROL CONNECTOR (SHORT TO GROUND)  .

   Measure the resistance between the ECM connector and engine ground.

   Connector & terminal 

   (E158) No. 29 - Engine ground:

   (E158) No. 27 - Engine ground:

   Is the resistance 1 MΩ or more?

   Yes:  Go to  5.

   No:  Repair the ground short circuit of harness between ECM connector and electronic throttle control connector.

5. CHECK POWER SUPPLY OF ELECTRONIC THROTTLE CONTROL  .
   1. Connect the connector to ECM.
   2. Turn the ignition switch to ON.
   3. Measure the voltage between electronic throttle control connector and engine ground.

      Connector & terminal 

      (E57) No. 5 (+) - Engine ground (-):

   Is the voltage 4.5 - 5.5 V?

   Yes:  Replace the electronic throttle control. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>THROTTLE BODY .

   No:  Replace the ECM. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>ENGINE CONTROL MODULE (ECM) .