April 5, 2026: LEMON Manuals is launched! Read the announcement.

DTC P0123 - Throttle/Pedal Position Sensor/Switch "A" Circuit High Input -

WARNING: This page is about a different variant/trim than selected.

DTC DETECTING CONDITION:
- Immediately at fault recognition
- GENERAL DESCRIPTION < Ref. to DTC P0123 - THROTTLE/PEDAL POSITION SENSOR/SWITCH "A" CIRCUIT HIGH INPUT - , Diagnostic Trouble Code (DTC) Detecting Criteria. >
TROUBLE SYMPTOM:
- Erroneous idling
- Engine stalls.
- Poor driving performance

WIRING DIAGRAM:

Fig 1: Throttle/Pedal Position Sensor/Switch Wiring Diagram
Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE

Step	Check	Yes	No
1 CHECK OUTPUT VOLTAGE OF SENSOR. Turn the ignition switch to ON. Read the data of main throttle sensor signals, using the Subaru Select Monitor. Shake the ECM harness and connector, engine harness connectors, electric throttle connector harness while monitoring value of voltage meter.	Is the measured value less than 4.63 V?	Go to step 2 .	Go to step 3 .
2 CHECK POOR CONTACT IN CONNECTORS. Check poor contact in connectors between ECM and electric throttle.	Is there poor contact in the connectors between ECM and electric throttle?	Repair the poor contact in connectors.	Connector has returned to a normal condition at this time. A temporary poor contact of the connector may be the cause.
3 CHECK HARNESS BETWEEN ECM AND ELECTRIC THROTTLE. Turn the ignition switch to OFF. Disconnect the connectors from ECM. Disconnect the connectors from electric throttle. Measure the resistance between ECM connector and electric throttle connector. Connector & terminal (B136) No. 18 - (E57) No. 6: (B136) No. 35 - (E57) No. 3:	Is the measured value less than 1 Ω?	Go to step 4 .	Repair the open of harness connector.
4 CHECK HARNESS BETWEEN ECM AND ELECTRIC THROTTLE. Connect the ECM connector. Measure the resistance between the electric throttle connector and engine ground. Connector & terminal (E57) No. 3 - Engine ground:	Is the measured value less than 1 Ω?	Go to step 5 .	Repair the poor contact in ECM connector. If the problem persists, replace the ECM. < Ref. to ENGINE CONTROL MODULE (ECM) . >
5 CHECK HARNESS BETWEEN ECM AND ELECTRIC THROTTLE. Turn the ignition switch to ON. Measure the voltage between electric throttle connector and engine ground. Connector & terminal (E57) No. 5 (+) - Engine ground (-): Shake the ECM harness and connector, engine harness connectors, while monitoring value of voltage meter.	Is the measured value more than 10 V?	Go to step 6 .	Repair the battery short of harness between ECM connector and electric throttle connector.
6 CHECK POWER SUPPLY TO SENSOR. Measure the voltage between the electric throttle connector and engine ground. Connector & terminal (E57) No. 6 (+) - Engine ground (-): Shake the ECM harness and connector, engine harness connectors, while monitoring value of voltage meter.	Is the measured value less than 10 V?	Go to step 7 .	Repair the short of harness between ECM connector and electric throttle connector.
7 CHECK HARNESS BETWEEN ECM AND ELECTRIC THROTTLE. Turn the ignition switch to OFF. Disconnect the connector from ECM. Measure the resistance between ECM connectors. Connector & terminal (B136) No. 18 - (B136) No. 16:	Is the measured value more than 1 MΩ?	Repair the poor contact in harness. Replace the electric throttle.	Repair the short of harness of power supply to sensor.