DTC P2127: Throttle/Pedal Position Sensor/Switch "E" Circuit Low: Notes

DTC detecting condition: 

Immediately at fault recognition

Trouble symptom: 

• Improper idling
• Poor driving performance
  CAUTION:

  • After servicing or replacing faulty parts, perform Clear Memory Mode Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>CLEAR MEMORY MODE>OPERATION , and inspection mode Refer to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>INSPECTION MODE>PROCEDURE ..
  • Use the check board when measuring the ECM terminal voltage and resistance.

Wiring diagram: 

Engine Electrical System Refer to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK HARNESS BETWEEN ECM AND ACCELERATOR PEDAL POSITION SENSOR CONNECTOR. 
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from ECM.
   3. Disconnect the connector from the accelerator pedal position sensor.
   4. Measure the resistance between the ECM connector and engine ground.

      Connector & terminal 

      (B134) No. 18 - Engine ground:

      (B134) No. 29 - Engine ground:

   Is the resistance 1 MΩ or more?

   Yes:  Go to  2.

   No:  Repair the short circuit to ground in harness between ECM connector and accelerator pedal position sensor connector.

2. CHECK SHORT CIRCUIT INSIDE THE ECM. 
   1. Connect the connector to ECM.
   2. Measure the resistance between accelerator pedal position sensor connector and chassis ground.

      Connector & terminal 

      (B315) No. 3 - Chassis ground:

   Is the resistance 1 MΩ or more?

   Yes:  Replace the accelerator pedal. Refer to SPEED CONTROL SYSTEMS (EXCEPT FOR STI)>ACCELERATOR PEDAL .

   No:  Repair the short circuit to ground in harness between ECM connector and accelerator pedal position sensor connector. Replace the ECM if defective. Refer to FUEL INJECTION (FUEL SYSTEMS) (EXCEPT FOR STI)>ENGINE CONTROL MODULE (ECM) .