DTC B1572 IMM Circuit Failure (Except Antenna Circuit): Wiring Diagram

Immobilizer system. See appropriate SYSTEM WIRING DIAGRAM article.

Fig 1: Immobilizer System - Wiring Diagram (IMM Circuit Failure)

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE

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. Connector & terminal (i84) 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. Measure the voltage between the body integrated unit connector terminal and chassis ground. Connector & terminal (i171) No. 17 (+) - 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 (B280) No. 1 - Chassis ground: (B281) No. 31 - Chassis ground: (i84) No. 1 - Chassis ground: (i171) No. 29 - 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 ECM. Measure the resistance between body integrated unit connector terminal and ECM connector terminal. Connector & terminal (B280) No. 31 - (B135) No. 25:	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. 31 (+) - Chassis ground (-):	Is the voltage 6 V or more?	Repair the harness between body integrated unit and ECM.	Go to step 7 .
7 CHECK COMMUNICATION CIRCUIT HARNESS. Measure the voltage between ECM connector terminal and engine ground. Connector & terminal (B135) No. 25 (+) - Engine ground (-):	Is the voltage 6 V or more?	Repair the harness between body integrated unit and ECM.	Go to step 8 .
8 CHECK ECM BY COMMUNICATION LINE CHECK. Connect the connector to ECM only. Start the communication line short check. Refer to COMMUNICATION LINE CHECK .	Is the communication line check OK?	Replace the body integrated unit. Refer to BODY INTEGRATED UNIT . Register all ignition keys (transponders). Refer to the "REGISTRATION MANUAL FOR IMMOBILIZER".	Replace the ECM. Refer to ENGINE CONTROL MODULE (ECM) . Perform the registration procedure next. Refer to the "REGISTRATION MANUAL FOR IMMOBILIZER".

NOTE: Refer to the following inspection when DTC is detected after inspection above. Refer to DTC B1578 METER FAILURE .