DTC B1572: IMM Circuit Except Antenna Circuit

DTC detecting condition: 

• Communication failure between body integrated unit and ECM
• Faulty antenna
• Incorrect immobilizer key (use of unregistered key in body integrated unit)
• Communication failure between ignition key and body integrated unit
  CAUTION: When the body integrated unit is replaced, registration of the immobilizer system is required. For details, refer to the "REGISTRATION MANUAL FOR IMMOBILIZER" provided as a separate volume.

Wiring diagram: 

Immobilizer system Refer to WIRING SYSTEM>IMMOBILIZER SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

• Engine type FA

  Engine electrical system Refer to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM .

  Courtesy of SUBARU OF AMERICA, INC.

• Engine type EJ

  Engine electrical system Refer to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM .

  Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC. 

   Read the DTC of the body integrated unit. Refer to IMMOBILIZER (DIAGNOSTICS)>READ DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC B1402, B1410 or B1411 displayed?

   Yes:  Perform the diagnosis for the displayed DTC B1402, B1410 or B1411.

   No:  Go to  2.

2. CHECK GROUNDING POINT. 

   Check the grounding point of the engine ground and chassis ground.

   Are there any loose connections, any foreign objects caught in the ground lines or contact surface, or any fluid stains?

   Yes:  Remove the foreign matters, and tighten to the specified torque. Then start the engine, and check that the fault was removed. Check DTC Refer to IMMOBILIZER (DIAGNOSTICS)>READ DIAGNOSTIC TROUBLE CODE (DTC) ., and when DTC B1572 is still displayed, Go to  3.

   No:  Go to  3.

3. CHECK FUSE. 
   1. Turn the ignition switch to OFF.
   2. Check the fuse.

   Is the check result OK?

   Yes:  Go to  4.

   No:  Replace the fuse. If the fuse blows out easily, repair the short circuit to power supply in harness between the battery and body integrated unit.

4. CHECK CURRENT DATA. 

   Confirm the current data «BATT voltage (control)» display of body integrated unit. Refer to BODY CONTROL SYSTEM (DIAGNOSTICS)>READ CURRENT DATA .

   Is the display 10 V or more?

   Yes:  Go to  5.

   No:  Go to  6.

5. CHECK CURRENT DATA. 

   Check the current data «Voltage of IGN» display of body integrated unit. Refer to BODY CONTROL SYSTEM (DIAGNOSTICS)>READ CURRENT DATA .

   Is the display 10 V or more?

   Yes:  Go to  8.

   No:  Go to  7.

6. CHECK BODY INTEGRATED UNIT BATTERY POWER SUPPLY CIRCUIT. 
   1. Turn the ignition switch to OFF.
   2. Disconnect the body integrated unit connector.
   3. Measure the voltage between body integrated unit connector and chassis ground.

      Connector & terminal 

      (i84) No. 6 (+) - Chassis ground (-):

   Is the voltage 10 V or more?

   Yes:  Go to  7.

   No:  Repair the open or short circuit of harness between the body integrated unit connector and fuse.

7. CHECK BODY INTEGRATED UNIT IGN POWER SUPPLY CIRCUIT. 
   1. Turn the ignition switch to ON.
   2. Measure the voltage between the body integrated unit connector terminal and chassis ground.

      Connector & terminal 

      (B281) No. 3 (+) - Chassis ground (-):

   Is the voltage 10 V or more?

   Yes:  Go to  8.

   No:  Repair the open or short circuit of harness between the body integrated unit connector and ignition switch.

8. CHECK BODY INTEGRATED UNIT GROUND CIRCUIT (OPEN CIRCUIT). 
   1. Turn the ignition switch to OFF.
   2. Measure the resistance between body integrated unit connector and chassis ground.

      Connector & terminal 

      (B280) No. 1 - Chassis ground:

      (i84) No. 1 - Chassis ground:

   Is the resistance less than 10 Ω?

   Yes:  Go to  9.

   No:  Repair the open circuit of harness between the body integrated unit connector and chassis ground.

9. CHECK GROUND CIRCUIT FOR ECM (OPEN CIRCUIT). 

   Measure the resistance between the ECM ground terminal and engine ground.

   Connector & terminal 

   Engine type: FA 

   (B134) No. 35 - Engine ground:

   (B134) No. 47 - Engine ground:

   (E159) No. 10 - Engine ground:

   (E159) No. 17 - Engine ground:

   (E159) No. 18 - Engine ground:

   (E159) No. 25 - Engine ground:

   (E159) No. 26 - Engine ground:

   Engine type: EJ 

   (B134) No. 3 - Engine ground:

   (B134) No. 4 - Engine ground:

   (B134) No. 6 - Engine ground:

   (B137) No. 1 - Engine ground:

   (B137) No. 3 - Engine ground:

   Is the resistance less than 10 Ω?

   Yes:  Go to  10.

   No:  Repair the ECM ground circuit.

10. CHECK HARNESS (OPEN CIRCUIT) BETWEEN BODY INTEGRATED UNIT AND ECM. 
    1. Disconnect the ECM connector.
    2. Measure the resistance between the body integrated unit connector and ECM.

       Connector & terminal 

       Engine type: FA 

       (B280) No. 31 - (E158) No. 43:

       Engine type: EJ 

       (B280) No. 31 - (B135) No. 25:

    Is the resistance less than 10 Ω?

    Yes:  Go to  11.

    No:  Repair the open circuit of harness between the body integrated unit connector and ECM.

11. CHECK COMMUNICATION LINE HARNESS (SHORT CIRCUIT TO POWER SUPPLY). 
    1. Disconnect the body integrated unit connector.
    2. Turn the ignition switch to ON.
    3. Measure the voltage between ECM connector and engine ground.

       Connector & terminal 

       Engine type: FA 

       (E158) No. 43 (+) - Engine ground (-):

       Engine type: EJ 

       (B135) No. 25 (+) - Engine ground (-):

    Is the voltage 6 V or more?

    Yes:  Repair the short circuit to power supply in harness between body integrated unit connector and ECM connector.

    No:  Go to  12.

12. CHECK COMMUNICATION CIRCUIT HARNESS (SHORT CIRCUIT TO GROUND). 
    1. Turn the ignition switch to OFF.
    2. Measure the resistance between the ECM connector and engine ground.

       Connector & terminal 

       Engine type: FA 

       (E158) No. 43 - Engine ground:

       Engine type: EJ 

       (B135) No. 25 - Engine ground:

    Is the resistance less than 10 Ω?

    Yes:  Repair the ground short circuit of harness between body integrated unit connector and ECM connector.

    No:  Go to  13.

13. CHECK ECM. 
    1. Replace the ECM. (Do not perform ECM registration.) Refer to FUEL INJECTION (FUEL SYSTEMS) (EXCEPT FOR STI)>ENGINE CONTROL MODULE (ECM) . Refer to FUEL INJECTION (FUEL SYSTEMS) (STI)>ENGINE CONTROL MODULE (ECM) .
    2. Connect all connectors.
    3. Turn the ignition switch to ON.
    4. Wait for 5 seconds.
    5. Read DTC of engine. Refer to IMMOBILIZER (DIAGNOSTICS)>READ DIAGNOSTIC TROUBLE CODE (DTC) .

    Is DTC B1572 displayed?

    Yes:  Replace the body integrated unit. Refer to SECURITY AND LOCKS>BODY INTEGRATED UNIT .

    No:  Register the ECM. Refer to the "REGISTRATION MANUAL FOR IMMOBILIZER" provided as a separate volume.