Other Than For C5

Diagnosis start condition:

Battery voltage is 10 V or more.
The remote engine starter was not used to start the engine.

DTC detecting condition:

Communication failure between body integrated unit and ECM

Trouble symptom:

Engine will not start.
The security indicator illuminates.

Impreza model

Wiring diagram:

Immobilizer system Ref. to WIRING SYSTEM (IMPREZA MODEL)>IMMOBILIZER SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

Crosstrek model

Wiring diagram:

Immobilizer system Ref. to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>IMMOBILIZER SYSTEM>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

CAUTION: When the body integrated unit or ECM is replaced, registration of the immobilizer system is required. For details, refer to the "REGISTRATION MANUAL FOR IMMOBILIZER" provided as a separate volume.

CHECK DTC .
1. Turn the ignition switch to ON.
2. Read the DTC of [Body Control] using the Subaru Select Monitor. Ref. to BODY CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .
Is DTC for [Body Control] displayed? (Current malfunction)

Yes: Perform the diagnosis for the displayed DTCs. Ref. to BODY CONTROL (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC)>LIST .

No: Go to 2.
CHECK GROUNDING POINT .
1. Turn the ignition switch to OFF.
2. Check the grounding point of the engine ground and chassis ground.
Is there any looseness? Are there any foreign matters caught on the ground or contact surface? Are there any oil-soiled areas?

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

No: Go to 3.
CHECK FUSE .
1. 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.
CHECK DATA MONITOR .
1. Turn the ignition switch to ON.
2. Using the Subaru Select Monitor, check the following items in the [Data Monitor] of [Body Control]. Ref. to BODY CONTROL (DIAGNOSTICS)>DATA MONITOR .
- BATT voltage (control)
Is the display 10 V or more?

Yes: Go to 5.

No: Go to 6.
CHECK DATA MONITOR .
Using the Subaru Select Monitor, check the following items in the [Data Monitor] of [Body Control]. Ref. to BODY CONTROL (DIAGNOSTICS)>DATA MONITOR .
- IGN voltage
Is the display 10 V or more?

Yes: Go to 8.

No: Go to 7.
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 and terminal
  
  (B281) No. 7 (+) - Chassis ground (-):
  
  (B280) No. 1 (+) - 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.
CHECK BODY INTEGRATED UNIT IGN POWER SUPPLY CIRCUIT .
1. Turn the ignition switch to ON.
2. Measure the voltage between F/B fuse No. 5 and chassis ground.
  Connector and terminal
  
  F/B fuse No. 5 (+) - 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.
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 and terminal
  
  (B287) No. 1 - Chassis ground:
  
  (i84) No. 4 - 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.
CHECK GROUND CIRCUIT FOR ECM (OPEN CIRCUIT) .
1. Disconnect the ECM connector.
2. Measure the resistance between the ECM connector and engine ground.
  Connector and terminal
  
  (B134) No. 69 - Engine ground:
  
  (B134) No. 70 - Engine ground:
  
  (B134) No. 72 - Engine ground:
  
  (B134) No. 71 - Engine ground:
Is: the resistance less than 10 Ω?

Yes: Go to 10.

No: Repair the open circuit in harness between ECM connector and chassis ground.
CHECK HARNESS (OPEN CIRCUIT) BETWEEN BODY INTEGRATED UNIT AND ECM .
Measure the resistance between the body integrated unit connector and ECM.

Connector and terminal

(B281) No. 14 - (B134) No. 6:

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.
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 and terminal
  
  (B134) No. 6 (+) - Chassis 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.
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 and terminal
  
  (B134) No. 6 - Chassis ground:
  
  (B134) No. 6 - 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.
CHECK ECM .
1. Replace the ECM. (Do not perform ECM registration.) Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO (EXCEPT FOR HEV))>ENGINE CONTROL MODULE (ECM) .
2. Connect all connectors.
3. Turn the ignition switch to ON.
4. Wait for 5 seconds.
5. Read the DTC of [Engine] using the Subaru Select Monitor. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.5)>DIAGNOSTIC TROUBLE CODE (DTC) . Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0 (EXCEPT FOR HEV))>DIAGNOSTIC TROUBLE CODE (DTC) . Ref. to ENGINE (DIAGNOSTICS) (H4DO(HEV))>DIAGNOSTIC TROUBLE CODE (DTC) .
Is DTC B1572 displayed? (Current malfunction)

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

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