DTC P1572 IMM Circuit Failure (Except Antenna Circuit): Wiring Diagram

WARNING: This page is about a different car, the 2012 Subaru Forester. However, it is still accessible from the selected car via links, so may be relevant.

Fig 1: Body Integrated Unit And ECM Communication Wiring Diagram

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE CHART

Step	Check	Yes	No
1 CHECK BODY INTEGRATED UNIT POWER SUPPLY CIRCUIT. Turn the ignition switch to OFF. Disconnect the connector from body integrated unit. Measure the voltage between the body integrated unit connector terminal and chassis ground. Connector & terminal (B280) No. 6 (+) - Chassis ground (-):	Is the voltage 10 V or more?	Go to step 2 .	Check the harness for open or short circuit between body integrated unit and fuse.
2 CHECK BODY INTEGRATED UNIT POWER SUPPLY CIRCUIT. Turn the ignition switch to ON. (engine OFF) Measure the voltage between the body integrated unit connector terminal and chassis ground. Connector & terminal (B280) No. 1 (+) - Chassis ground (-):	Is the voltage 10 V or more?	Go to step 3 .	Check the harness for open or short circuit between the body integrated unit and ignition switch.
3 CHECK BODY INTEGRATED UNIT GROUND CIRCUIT. Turn the ignition switch to OFF. Measure the resistance between the body integrated unit connector terminal and chassis ground. Connector & terminal (i84) No. 28 - Chassis ground: (B280) No. 17 - Chassis ground: (B281) No. 20 - Chassis ground: (B279) No. 27 - Chassis ground:	Is the resistance less than 10 Ω?	Go to step 4 .	Repair the open circuit of the body integrated unit ground circuit.
4 CHECK GROUND CIRCUIT FOR ECM. Measure the resistance between the ECM ground terminal and engine ground.	Is the resistance less than 10 Ω?	Go to step 5 .	Repair the ECM ground circuit.
5 CHECK HARNESS BETWEEN BODY INTEGRATED UNIT AND ECM. Disconnect the connector from the ECM and body integrated unit. Measure the resistance between body integrated unit connector terminal and ECM connector terminal. Connector & terminal (B280) No. 4 - (B135) No. 25: (B280) No. 15 - (B135) No. 24:	Is the resistance less than 10 Ω?	Go to step 6 .	Repair the open circuit of the harness between the body integrated unit and ECM.
6 CHECK COMMUNICATION CIRCUIT HARNESS. Turn the ignition switch to ON. Measure the voltage between the body integrated unit connector terminal and chassis ground. Connector & terminal (B280) No. 4 (+) - Chassis ground (-): (B280) No. 15 (+) - Chassis ground (-):	Is the voltage 0 V?	Go to step 7 .	Repair the harness between body integrated unit and ECM.
7 CHECK COMMUNICATION CIRCUIT HARNESS. Measure the voltage between ECM connector terminal and engine ground. Connector & terminal (B135) No. 24 (+) - Chassis ground (-): (B135) No. 25 (+) - Chassis ground (-):	Is the voltage 0 V?	Go to step 8 .	Repair the harness between body integrated unit and ECM.
8 CHECK ECM BY COMMUNICATION SHORT CHECK. Connect the connector to ECM. Disconnect the connector from body integrated unit. Start the communication short check. < Refer to COMMUNICATION LINE CHECK , OPERATION, Subaru Select Monitor. >	Is the communication short check OK?	Replace the body integrated unit < Refer to BODY INTEGRATED UNIT . > Register all ignition keys (transponders). Refer to the PC application help for Subaru Select Monitor.	Replace the ECM. < Refer to ENGINE CONTROL MODULE (ECM) . > Perform the registration procedure next. Refer to the PC application help for Subaru Select Monitor.

NOTE: Refer to the following inspection when DTC is detected after inspection above. < Refer to DTC P1578 METER FAILURE , Diagnostic Procedure with Diagnostic Trouble Code (DTC). >