IMMOBILIZER (DIAGNOSTICS) > Diagnostic Procedure with Diagnostic Trouble Code (DTC)

DTC P1572 IMM CIRCUIT FAILURE (EXCEPT ANTENNA CIRCUIT)

DTC DETECTING CONDITION:

Communication failure between body integrated unit and ECM

WIRING DIAGRAM:

STEPCHECKYESNO

1.CHECK BODY INTEGRATED UNIT POWER SUPPLY CIRCUIT.

1) Turn the ignition switch to OFF.

2) Disconnect the harness connector from the body integrated unit.

3) Measure the voltage between the body integrated unit harness connector terminal and chassis ground.

Connector & terminal

(B280) No. 6 (+) — Chassis ground (−):

Is the voltage 10 V or more?

Check the harness for open or short circuit between the body integrated unit and fuse.

2.CHECK BODY INTEGRATED UNIT POWER SUPPLY CIRCUIT.

1) Turn the ignition switch to ON. (engine OFF)

2) Measure the voltage between the body integrated unit harness connector terminal and chassis ground.

Connector & terminal

(B280) No. 1 (+) — Chassis ground (−):

Is the voltage 10 V or more?

Check the harness for open or short circuit between the body integrated unit and ignition switch.

3.CHECK BODY INTEGRATED UNIT GROUND CIRCUIT.

1) Turn the ignition switch to OFF.

2) Measure the resistance between the body integrated unit harness connector terminal and chassis ground.

Connector & terminal

(B280) No. 17 — Chassis ground:

(B281) No. 20 — Chassis ground:

(B279) No. 27 — Chassis ground:

Is the resistance less than 10 Ω?

Repair the open circuit of the body integrated unit ground circuit.

4.CHECK HARNESS BETWEEN BODY INTEGRATED UNIT AND ECM.

1) Disconnect the harness connector from the ECM and body integrated unit.

2) Measure the resistance between the body integrated unit harness connector and ECM harness connector terminals.

Connector & terminal

Turbo model

(B280) No. 4 — (B136) No. 26:

Non-turbo MODEL

(B280) No. 4 — (B135) No. 23:

Is the resistance less than 10 Ω?

Repair the open circuit of the harness between the body integrated unit and ECM.

5.CHECK HARNESS BETWEEN BODY INTEGRATED UNIT AND ECM.

Measure the resistance between the body integrated unit harness connector and ECM harness connector terminals.

Connector & terminal

Turbo model

(B280) No. 15 — (B136) No. 34:

NON-TURBO MODEL

(B280) No. 15 — (B135) No. 31:

Is the resistance less than 10 Ω?

Repair the open circuit of the harness between the body integrated unit and ECM.

6.CHECK COMMUNICATION CIRCUIT HARNESS.

1) Turn the ignition switch to ON. (engine OFF)

2) Measure the voltage between the body integrated unit harness connector terminal and chassis ground.

Connector & terminal

(B280) No. 4 (+) — Chassis ground (−):

(B280) No. 15 (+) — Chassis ground (−):

Is the voltage 0 V?

Because the battery voltage or ignition switch “ON” circuit is shorted, repair the harness between the body integrated unit and ECM.

7.CHECK COMMUNICATION CIRCUIT HARNESS.

Measure the voltage between the ECM harness connector terminal and engine ground.

Connector & terminal

Turbo model

(B136) No. 26 (+) — Engine ground (−):
(B136) No. 34 (+) — Engine ground (−):

Non-turbo model

(B135) No. 23 (+) — Engine ground (−):
(B135) No. 31 (+) — Engine ground (−):

Is the voltage 0 V?

Because the battery voltage or ignition switch “ON” circuit is shorted, repair the harness between the body integrated unit and ECM.

8.CHECK ECM BY COMMUNICATION LINE CHECK.

1) Connect the harness connector to the ECM.

2) Disconnect the harness connector from the body integrated unit.

3) Start the communication line short check.

Is the communication line check OK?

Replace the body integrated unit. Replace all ignition keys (including the transponder). Execute the registration procedure next. Refer to the “PC application help for Subaru Select Monitor”.

Replace the ECM. Next, execute the registration procedure. Refer to the “PC application help for Subaru Select Monitor”.