Wiring Diagram:

Fig 1: DTC P0122 - Throttle/Pedal Position Sensor/Switch "A" Circuit Low Input -

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC STEPS DTC P0122

Step	Check	Yes	No
1. CHECK CURRENT DATA. Start engine. Read data of throttle position sensor signal using Subaru Select Monitor or OBD-II general scan tool. NOTE: Subaru Select Monitor For detailed operation procedure, refer to the "READ CURRENT DATA FOR ENGINE". < Ref. to SUBARU SELECT MONITOR . > OBD-II general scan tool For detailed operation procedures, refer to the OBD-II General Scan Tool Instruction Manual.	Is the measured value less than 0.1 V?	Go to step 2.	Even if MIL lights up, the circuit has returned to a normal condition at this time. A temporary poor contact of the connector may be the cause. NOTE: In this case, repair the following: Poor contact in throttle position sensor connector Poor contact in ECM connector Poor contact in coupling connector
2. CHECK INPUT SIGNAL FOR ECM. Measure voltage between ECM connector and chassis ground while throttle valve is fully closed. Connector & terminal (B135) No. 3 (+) - Chassis ground (-):	Is the measured value more than 4.5 V?	Go to step 4.	Go to step 3.
3. CHECK INPUT SIGNAL FOR ECM. Measure voltage between ECM connector and chassis ground. Connector & terminal (B136) No. 3 (+) - Chassis ground (-):	Is the measured value more than 4.5 V when shaking harness and connector of ECM?	Repair poor contact in ECM connector.	Contact with SOA (distributor) service. NOTE: Inspection by DTM is required, because probable cause is deterioration of multiple parts.
4. CHECK INPUT SIGNAL FOR ECM. Measure voltage between ECM connector and chassis ground. Connector & terminal (B135) No. 13 (+) - Chassis ground (-):	Is the measured value less than 0.1 V?	Go to step 6.	Go to step 5.
5. CHECK INPUT SIGNAL FOR ECM. (USING SUBARU SELECT MONITOR.) Measure voltage between ECM connector and chassis ground.	Is the measured value more than 0.1 V when shaking harness and connector of ECM?	Repair poor contact in ECM connector.	Go to step 6.
6. CHECK HARNESS BETWEEN ECM AND THROTTLE POSITION SENSOR CONNECTOR. Turn ignition switch to OFF. Disconnect connectors from throttle position sensor. Turn ignition switch to ON. Measure voltage between throttle position sensor connector and engine ground. Connector & terminal (E13) No. 4 (+) - Engine ground (-):	Is the measured value more than 4.5 V?	Go to step 7.	Repair harness and connector. NOTE: In this case, repair the following: Open circuit in harness between throttle position sensor and ECM connector Poor contact in throttle position sensor connector Poor contact in ECM connector Poor contact in coupling connector Poor contact in joint connector
7. CHECK HARNESS BETWEEN ECM AND THROTTLE POSITION SENSOR CONNECTOR. Turn ignition switch to OFF. Measure resistance of harness between ECM connector and throttle position sensor connector. Connector & terminal (B135) No. 13 - (E13) No. 3:	Is the measured value less than 1 Ω?	Go to step 8.	Repair harness and connector. NOTE: In this case, repair the following: Open circuit in harness between throttle position sensor and ECM connector Poor contact in ECM connector Poor contact in throttle position sensor connector Poor contact in coupling connector
8. CHECK HARNESS BETWEEN ECM AND THROTTLE POSITION SENSOR CONNECTOR. Measure resistance of harness between throttle position sensor connector and engine ground. Connector & terminal (E13) No. 3 - Engine ground:	Is the measured value more than 1 MΩ?	Go to step 9.	Repair ground short circuit in harness between throttle position sensor and ECM connector.
9. CHECK POOR CONTACT. Check poor contact in throttle position sensor connector.	Is there poor contact in throttle position sensor connector?	Repair poor contact in throttle position sensor connector.	Replace throttle position sensor. Ref. to THROTTLE POSITION SENSOR .