Wiring Diagram:

Fig 1: Wiring Diagram - DTC P2123 Throttle/Pedal Position Sensor/Switch

Courtesy of SUBARU OF AMERICA, INC.

DTC P2123 DIAGNOSTIC PROCEDURE

Step	Check	Yes	No
1. CHECK OUTPUT VOLTAGE OF ACCELERATOR POSITION SENSOR. Turn the ignition switch to ON. Read the data of main accelerator position sensor signals, using Subaru Select Monitor. NOTE: Subaru Select Monitor For detailed operation procedure, refer to "READ CURRENT DATA FOR ENGINE". < Ref. to , SUBARU SELECT MONITOR . >	Is the voltage less than 4.8 V?	Go to step 2.	Go to step 3.
2. CHECK POOR CONTACT IN CONNECTORS. Check poor contact in connectors between ECM and accelerator position sensor.	Is there any poor contact in connectors between ECM and accelerator position sensor?	Repair the poor contact in connectors.	Connector has returned to its normal condition at this time. A temporary poor contact in the connector might have been the cause.
3. CHECK HARNESS BETWEEN ECM AND ACCELERATOR POSITION SENSOR. Turn the ignition switch to OFF. Disconnect the connector from ECM. Disconnect the connector from accelerator position sensor. Measure the resistance between ECM connector and accelerator position sensor. Connector & terminal (B136) 34 - (B315) No. 4:	Is the resistance less than 1 Ω?	Go to step 4.	Repair the open harness connector.
4. CHECK HARNESS BETWEEN ECM AND ACCELERATOR POSITION SENSOR. Connect the ECM connector. Measure the resistance between accelerator position sensor and chassis ground. Connector & terminal (B315) 4 - Chassis ground:	Is the resistance less than 5 Ω?	Go to step 5.	Repair the poor contact in ECM connector. If problem persists, replace the ECM. < Ref. to ENGINE CONTROL MODULE (ECM) . >
5. CHECK HARNESS BETWEEN ECM AND ACCELERATOR POSITION SENSOR. Connect the ECM connector. Turn the ignition switch to ON. Measure the voltage between accelerator position sensor connector and chassis ground. Connector & terminal (B315) 5 (+) - Chassis ground (-):	Is the voltage less than 6 V?	Go to step 6.	Repair the battery short of harness between ECM connector and accelerator position sensor.
6. CHECK HARNESS BETWEEN ECM AND ACCELERATOR POSITION SENSOR. Turn the ignition switch to OFF. Disconnect the connector from ECM. Measure the resistance between ECM connectors. Connector & terminal (B136)No. 17-(B136)No. 15: (B136)No. 17 - (B136)No. 16:	Is the resistance more than 1 MΩ?	Repair the poor contact in electronic throttle control connector. If problem persists, replace the electronic throttle control.	Repair the short to sensor power supply.