DTC P2122 Throttle/Pedal Position Sensor/Switch "D" Circuit Low 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 P2122 THROTTLE/PEDAL POSITION SENSOR/SWITCH "D" CIRCUIT LOW 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 Low 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. Measure the voltage between ECM connector terminals. Connector & terminal (B135) No. 23 (+) - (B135) No. 29 (-): Check the voltage change by shaking the harness and connector of the accelerator pedal position sensor, and the ECM harness and connector.	Is the voltage more than 0.4 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 of ECM connector and accelerator pedal position sensor connector. Connector & terminal (B135) No. 21 - (B315) No. 4: (B135) No. 23 - (B315) No. 6:	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. Measure the resistance between ECM connector and chassis ground. Connector & terminal (B135) No. 21 - Chassis ground: (B135) No. 23 - Chassis ground:	Is the resistance more than 1 MΩ?	Go to step 5.	Repair the chassis short circuit of harness.
5 CHECK POWER SUPPLY OF 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 change by shaking the harness and connector of ECM while monitoring the value with voltage meter.	Is the voltage 4.5 - 5.5 V?	Go to step 6.	Repair poor contact in ECM connector. Replace the ECM if defective. <Ref. to ENGINE CONTROL MODULE (ECM) . >
6 CHECK ACCELERATOR PEDAL POSITION SENSOR. Measure the resistance of accelerator pedal position sensor. Terminals No. 4 - No. 5:	Is the resistance between 1.2 and 4.8 kΩ?	Go to step 7.	Replace the accelerator pedal position sensor.
7 CHECK ACCELERATOR PEDAL POSITION SENSOR. Measure the resistance of accelerator pedal position sensor without depressing the accelerator pedal. Terminals No. 6 - No. 5:	Is the resistance between 0.2 and 1.0 kΩ?	Go to step 8.	Replace the accelerator pedal position sensor.
8 CHECK ACCELERATOR PEDAL POSITION SENSOR. Measure the resistance of accelerator pedal position sensor with depressing the accelerator pedal. Terminals No. 6 - No. 5:	Is the resistance between 0.5 and 2.5 kΩ?	Repair poor contact in ECM connector. Replace the ECM if defective. <Ref. to ENGINE CONTROL MODULE (ECM) . >	Replace the accelerator pedal position sensor.