DTC P2123: Throttle/Pedal Position Sensor/Switch "D" Circuit High: 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 Ref. to ENGINE (DIAGNOSTICS) (EXCEPT FOR STI)>Clear Memory Mode>OPERATION , and inspection mode Ref. 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 Ref. to WIRING SYSTEM>Engine Electrical System>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

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 of harness between ECM connector and accelerator pedal position sensor connector.
  Connector & terminal
  
  (B134) No. 17 - (B315) No. 6:
  
  (B134) No. 31 - (B315) No. 5:
Is the resistance less than 1 Ω?

Yes: Go to 2

No: Repair the open circuit of harness between ECM connector and accelerator pedal position sensor connector.
CHECK HARNESS BETWEEN ECM AND ACCELERATOR PEDAL POSITION SENSOR CONNECTOR .
1. Connect the connector to ECM.
2. Measure the resistance between accelerator pedal position sensor connector and chassis ground.
  Connector & terminal
  
  (B315) No. 5 - Chassis ground:
Is the resistance less than 5 Ω?

Yes: Go to 3

No: Repair the harness and connector.
NOTE:
In this case, repair the following item:
- Open circuit of harness between ECM connector and engine ground
- Poor contact of ECM connector
- Poor contact of coupling connector
CHECK HARNESS BETWEEN ECM AND ACCELERATOR PEDAL POSITION SENSOR CONNECTOR .
1. Turn the ignition switch to ON.
2. Measure the voltage between accelerator pedal position sensor connector and chassis ground.
  Connector & terminal
  
  (B315) No. 6 (+) - Chassis ground (-):
Is the voltage 5 V or more?

Yes: Repair the short circuit to power supply in harness between ECM connector and accelerator pedal position sensor connector.

No: Go to 4
CHECK HARNESS BETWEEN ECM AND ACCELERATOR PEDAL POSITION SENSOR CONNECTOR .
1. Turn the ignition switch to OFF.
2. Disconnect the connector from ECM.
3. Measure the resistance between ECM connectors.
  Connector & terminal
  
  (B134) No. 17 - (B134) No. 30:
Is the resistance 1 MΩ or more?

Yes: Repair the poor contact of accelerator pedal position sensor connector. Replace the accelerator pedal if defective. Ref. to SPEED CONTROL SYSTEMS(EXCEPT FOR STI)>Accelerator Pedal .

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