Wiring Diagram:

Fig 1: Wiring Diagram - DTC P2128 Throttle/Pedal Position Sensor/Switch "E" Circuit High Input

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE (DTC P2128)

Step	Check	Yes	No
1 CHECK ACCELERATOR POSITION SENSOR OUTPUT. Turn the ignition switch to ON. Read the data of sub accelerator position sensor signal using Subaru Select Monitor. NOTE: Subaru Select Monitor For detailed operation procedure, refer to the "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. Check poor contact in connector between ECM and accelerator position sensor.	Is there poor contact?	Repair the poor contact.	Temporary poor contact occurred, but it is normal at present.
3 CHECK HARNESS BETWEEN ECM AND ACCELERATOR POSITION SENSOR. Turn the ignition switch to OFF. Disconnect the connector from ECM. Disconnect the connector from the accelerator position sensor. Measure the resistance between ECM connector and accelerator position sensor connector. Connector & terminal (B136) No. 35 - (B315) No. 6:	Is the resistance less than 1 ?	Go to step 4.	Repair the open circuit of harness connector.
4 CHECK HARNESS BETWEEN ECM AND ACCELERATOR POSITION SENSOR. Connect the ECM connector. Measure the resistance between accelerator position sensor connector and chassis ground. Connector & terminal (B315) No. 6 - Chassis ground:	Is the resistance less than 5 ?	Go to step 5.	Repair the poor contact in ECM connector. Replace the ECM if defective. < 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) No. 2 (+) - Chassis ground (-):	Is the voltage less than 6 V?	Go to step 6.	Repair the battery short circuit in harness between ECM connector and accelerator position sensor connector.
6 CHECK HARNESS BETWEEN ECM AND ACCELERATOR POSITION SENSOR. Turn the ignition switch to OFF. Measure the resistance between ECM connector terminals. Connector & terminal (B137) No. 28 - (B137) No. 15: (B137) No. 28 - (B137) No. 16:	Is the resistance more than 1 M?	Repair the poor contact in accelerator position sensor connector. Replace the accelerator position sensor if defective.	Repair the short circuit to sensor power supply.