DTC P0123: Throttle/Pedal Position Sensor/Switch "A" Circuit High: Notes

-
DTC detecting condition:

Immediately at fault recognition

Trouble symptom:
- Improper idling
- Engine stalls.
- Poor driving performance
Wiring diagram:

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

Courtesy of SUBARU OF AMERICA, INC.

CAUTION: Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>General Description>PREPARATION TOOL>HOW TO USE CHECK BOARD .

NOTE: After the faulty parts are repaired or replaced, perform the final check in Basic Diagnostic Procedure. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>Basic Diagnostic Procedure>PROCEDURE .

CHECK HARNESS BETWEEN ECM AND ELECTRONIC THROTTLE CONTROL CONNECTOR (OPEN) .
1. Turn the ignition switch to OFF.
2. Disconnect the connector from ECM.
3. Disconnect the connectors from electronic throttle control.
4. Measure the resistance of harness between ECM connector and electronic throttle control connector.
  Connector & terminal
  
  (E158) No. 34 - (E57) No. 1:
  
  (E158) No. 20 - (E57) No. 3:
Is the resistance less than 1 Ω?

Yes : Go to 2.

No : Repair the open circuit of harness between ECM connector and electronic throttle control connector.
CHECK HARNESS BETWEEN ECM AND ELECTRONIC THROTTLE CONTROL CONNECTOR (OPEN) .
1. Connect the connector to ECM.
2. Measure the resistance between electronic throttle control connector and engine ground.
  Connector & terminal
  
  (E57) No. 3 - Engine ground:
Is the resistance less than 5 Ω?

Yes : Go to 3.

No : Repair the following item.
- Open circuit of harness between ECM connector and engine ground
- Poor contact of ECM connector
CHECK HARNESS BETWEEN ECM AND ELECTRONIC THROTTLE CONTROL CONNECTOR (SHORT TO POWER SUPPLY) .
1. Turn the ignition switch to ON.
2. Measure the voltage between electronic throttle control connector and engine ground.
  Connector & terminal
  
  (E57) No. 1 (+) - Engine ground (-):
Is the voltage 5 V or more?

Yes : Repair the short circuit to power in the harness between ECM connector and electronic throttle control connector.

No : Go to 4.
CHECK HARNESS BETWEEN ECM AND ELECTRONIC THROTTLE CONTROL CONNECTOR (SHORT BETWEEN LINES) .
1. Turn the ignition switch to OFF.
2. Disconnect the connector from ECM.
3. Measure the resistance between ECM connectors.
  Connector & terminal
  
  (E158) No. 34 - (E158) No. 49:
Is the resistance 1 MΩ or more?

Yes : Repair the poor contact of electronic throttle control connector. Replace the electronic throttle control if defective. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>THROTTLE BODY .

No : Repair the line-to-line short circuit between ECM connector and electronic throttle control connector.