Wiring Diagram:

Fig 1: Wiring Diagram - DTC P2021 Intake Manifold Runner Position Sensor / Switch Circuit Low (Bank 2)

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE (DTC P2021)

Step	Check	Yes	No
1 CHECK CURRENT DATA. Start the engine. Read the data of tumble generator valve 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 procedure, refer to the OBD-II general scan tool instruction manual .	Is the voltage less than 0.1 V?	Go to step 2.	Even if malfunction indicator light 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 the voltage between ECM connector and chassis ground while tumble generator valve is fully closed. Connector & terminal (B136) No. 16 (+) - Chassis ground (-):	Is the voltage more than 4.5 V?	Go to step 4.	Go to step 3.
3 CHECK INPUT SIGNAL FOR ECM. Measure the voltage between ECM connector and chassis ground. Connector & terminal (B136) No. 16 (+) - Chassis ground (-):	Shake the ECM harness and connector, while monitoring value of voltage meter. Does the voltage change?	Repair the poor contact in ECM connector.	Contact your SOA Service Center.
4 CHECK INPUT SIGNAL FOR ECM. Measure the voltage between ECM connector and chassis ground. Connector & terminal (B136) No. 26 (+) - Chassis ground (-):	Is the voltage less than 0.1 V?	Go to step 6.	Go to step 5.
5 CHECK INPUT SIGNAL FOR ECM. (USING SUBARU SELECT MONITOR) Measure the voltage between ECM connector and chassis ground.	Shake the ECM harness and connector, while monitoring value of Subaru Select Monitor. Does the voltage change?	Repair the poor contact in ECM connector.	Go to step 6.
6 CHECK HARNESS BETWEEN ECM AND TUMBLE GENERATOR VALVE POSITION SENSOR CONNECTOR. Turn the ignition switch to OFF. Disconnect the connectors from tumble generator valve position sensor. Turn the ignition switch to ON. Measure the voltage between tumble generator valve position sensor connector and engine ground. Connector & terminal (E66) No. 1 (+) - Engine ground (-):	Is the voltage more than 4.5 V?	Go to step 7.	Repair the harness and connector. NOTE: In this case, repair the following: Open circuit in harness between tumble generator valve position sensor and ECM connector Poor contact in tumble generator valve position sensor connector Poor contact in ECM connector Poor contact in coupling connector Poor contact in joint connector
7 CHECK HARNESS BETWEEN ECM AND TUMBLE GENERATOR VALVE POSITION SENSOR CONNECTOR. Turn the ignition switch to OFF. Measure the resistance of harness between ECM connector and tumble generator valve position sensor connector. Connector & terminal (B136) No. 26 - (E66) No. 3:	Is the resistance less than 1 ?	Go to step 8.	Repair the harness and connector. NOTE: In this case, repair the following: Open circuit in harness between tumble generator valve position sensor and ECM connector Poor contact in ECM connector Poor contact in tumble generator valve position sensor connector Poor contact in coupling connector
8 CHECK HARNESS BETWEEN ECM AND TUMBLE GENERATOR VALVE POSITION SENSOR CONNECTOR. Measure the resistance of harness between tumble generator valve position sensor connector and engine ground. Connector & terminal (E66) No. 3 - Engine ground:	Is the resistance more than 1 M?	Go to step 9.	Repair the ground short circuit in harness between tumble generator valve position sensor and ECM connector.
9 CHECK POOR CONTACT. Check poor contact in tumble generator valve position sensor connector.	Is there poor contact in tumble generator valve position sensor connector?	Repair the poor contact in tumble generator valve position sensor connector.	Replace the tumble generator valve position sensor. < Ref. to TUMBLE GENERATOR VALVE POSITION SENSOR . >