Diagnostic Procedure for Subaru Select Monitor Communication: Inspection

WARNING: This page is about a different car, the 2022 Subaru WRX. However, it is still accessible from the selected car via links, so may be relevant.

Trouble symptom:

Cannot communicate with [Body Control].

Detecting condition:

Defective harness connector
Power supply circuit malfunction
Defective CAN communication circuit
Defective Subaru Select Monitor

Wiring diagram:

Door lock control system Ref. to WIRING SYSTEM>DOOR LOCK CONTROL SYSTEM>WIRING DIAGRAM
CAN communication system Ref. to WIRING SYSTEM>CAN COMMUNICATION SYSTEM>WIRING DIAGRAM

Courtesy of SUBARU OF AMERICA, INC.

CAUTION:

Before performing diagnosis, refer to "CAUTION" in "General Description". Ref. to BODY CONTROL (DIAGNOSTICS)>GENERAL DESCRIPTION>CAUTION

CHECK POWER SUPPLY CIRCUIT .
Connect the interface for Subaru Select Monitor to the data link connector.

Does the interface for Subaru Select Monitor turn on?

Yes : Go to 4.

No : Go to 2.
CHECK POWER SUPPLY CIRCUIT .
1. Turn the ignition switch to ON.
2. Using the tester, measure the voltage between data link connector and chassis ground.
  Connector & terminal
  
  (i221) No. 8 (+) - Chassis ground (-):
  
  (i221) No. 16 (+) - Chassis ground (-):
Is the voltage 10 V or more?

Yes : Go to 3.

No : Repair the power supply circuit.
NOTE:
In this case, repair the following item:
- Open or ground short circuit of harness between battery and data link connector
- Blown out of fuse (M/B No. 2, F/B fuse No. 3)
CHECK HARNESS BETWEEN DATA LINK CONNECTOR AND CHASSIS GROUND (OPEN) .
1. Turn the ignition switch to OFF.
2. Using the tester, measure the resistance between data link connector and chassis ground.
  Connector & terminal
  
  (i221) No. 4 - Chassis ground:
  
  (i221) No. 5 - Chassis ground:
Is the resistance less than 5 Ω?

Yes : Check for poor contact of the data link connector, and repair a fault, if any. When no fault is found, Go to 4.

No : Repair the harness and connector.
CHECK SUBARU SELECT MONITOR .
1. Connect the Subaru Select Monitor to a normal vehicle.
2. Start the engine and establish communication between the Subaru Select Monitor and vehicle.
Is communication possible?

Yes : Go to 5.

No : Use another Subaru Select Monitor because the CAN communication circuit of the Subaru Select Monitor is faulty.
CHECK LAN SYSTEM .
Perform the diagnosis for LAN system. Ref. to LAN SYSTEM (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE

Is the check result OK?

Yes : Go to 6.

No : Perform the inspection according to the diagnosis for LAN system.
CHECK CONNECTOR .
Check poor contact of body integrated unit connector, data link connector and coupling connector.

Is the check result OK?

Yes : Go to 7.

No : Repair the connector.
CHECK FUSE .
1. Turn the ignition switch to OFF.
2. Check the fuse. Ref. to WIRING SYSTEM>INTERIOR LIGHT SYSTEM>WIRING DIAGRAM
Is the check result OK?

Yes : Go to 8.

No : Replace the fuse. If the replaced fuse blows out easily, repair the ground short circuit in the harness between the body integrated unit and fuse.
CHECK BODY INTEGRATED UNIT CONNECTOR POWER SUPPLY CIRCUIT (OPEN) .
1. Disconnect the connector from body integrated unit.
2. Turn the ignition switch to ON.
3. Measure the voltage between body integrated unit connector and chassis ground using tester.
  Connector & terminal
  
  (B73) No. 7 (+) - Chassis ground (-):
  
  (B71) No. 1 (+) - Chassis ground (-):
Is the voltage 10 V or more?

Yes : Go to 9.

No : Check the harness for open or short circuit between body integrated unit and fuse.
CHECK BODY INTEGRATED UNIT GROUND CIRCUIT (OPEN CIRCUIT) .
Measure the resistance of harness between body integrated unit connector and chassis ground using tester.

Connector & terminal

(i81) No. 4 - Chassis ground:

(B72) No. 1 - Chassis ground:

Is the resistance less than 5 Ω?

Yes : Check the connection between the data link connector and Subaru Select Monitor.

No : Repair the harness for ground line.