DTC P2123 Throttle/Pedal Position Sensor/Switch "D" Circuit High Input

WARNING: This page is about a different car, the 2006 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.

DTC DETECTING CONDITION:

Immediately at fault recognition
GENERAL DESCRIPTION <Ref. to DTC P2123 THROTTLE/PEDAL POSITION SENSOR/SWITCH "D" CIRCUIT HIGH INPUT , Diagnostic Trouble Code (DTC) Detecting Criteria. >

TROUBLE SYMPTOM:

Improper idling
Poor driving performance

CAUTION: After repairing or replacing the defective part, carry out the Clear Memory Mode <Ref. to OPERATION , CLEAR MEMORY MODE. > and Inspection Mode <Ref. to PROCEDURE , INSPECTION MODE. >

WIRING DIAGRAM:

Fig 1: Identifying Throttle/Pedal Position Sensor/Switch "D" Circuit High Input - Wiring Diagram

Courtesy of SUBARU OF AMERICA, INC.

TROUBLESHOOTING CHART

Step	Check	Yes	No
1 CHECK ACCELERATOR PEDAL POSITION SENSOR OUTPUT. Turn the ignition switch to ON. Read the data of main accelerator pedal position sensor signal using Subaru Select Monitor. Check the voltage change while shaking the ECM harness and connector, engine harness and connector, and the accelerator pedal position sensor connector harness.	Is the voltage less than 4.8 V?	Go to step 2.	Go to step 3.
2 CHECK POOR CONTACT. Check poor contact of connector between ECM and accelerator pedal 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 PEDAL POSITION SENSOR. Turn the ignition switch to OFF. Disconnect the connectors from ECM. Disconnect the connectors from accelerator pedal position sensor. Measure the resistance between ECM connector and accelerator pedal position sensor connector. Connector & terminal (B135) No. 29 - (B315) No. 5:	Is the resistance less than 1 Ω?	Go to step 4.	Repair the open circuit of harness connector.
4 CHECK HARNESS BETWEEN ECM AND ACCELERATOR PEDAL POSITION SENSOR. Connect the ECM connector. Measure the resistance between accelerator pedal position sensor connector and engine ground. Connector & terminal (B315) No. 5 - Engine ground:	Is the resistance less than 5 Ω?	Go to step 5.	Repair poor contact in ECM connector. Replace the ECM if defective. <Ref. to ENGINE CONTROL MODULE (ECM) . >
5 CHECK HARNESS BETWEEN ECM AND ACCELERATOR PEDAL POSITION SENSOR. Connect the ECM connector. Turn the ignition switch to ON. Measure the voltage between accelerator pedal position sensor connector and engine ground. Connector & terminal (B315) No. 4 (+) - Engine ground (-): Check the voltage is above the specified value when shaking the harness and connector of ECM while monitoring the value with voltage meter.	Is the voltage more than 6 V?	Go to step 6.	Repair the battery short circuit of harness between ECM connector and accelerator pedal position sensor connector.
6 CHECK POWER SUPPLY OF ACCELERATOR PEDAL POSITION SENSOR. Measure the voltage between accelerator pedal position sensor connector and engine ground. Connector & terminal (B315) No. 6 (+) - Engine ground (-): Check the voltage is below the specified value when shaking the harness and connector of ECM while monitoring the value with voltage meter.	Is the voltage less than 4.8 V?	Go to step 7.	Repair the short circuit of harness between ECM connector and accelerator pedal position sensor connector.
7 CHECK HARNESS BETWEEN ECM AND ACCELERATOR PEDAL POSITION SENSOR. Turn the ignition switch to OFF. Connect the accelerator pedal position sensor connector. Turn the ignition switch to ON. Measure the voltage between ECM connector and chassis ground. Connector & terminal (B135) No. 23 (+) - Chassis ground (-):	Is the voltage 4.8 V?	Repair poor contact in ECM connector. Replace the ECM if defective. <Ref. to ENGINE CONTROL MODULE (ECM) . >	Repair the poor contact of accelerator pedal position sensor connector. Replace the accelerator pedal position sensor if defective.