Diagnostic Procedure for Subaru Select Monitor Communication: Inspection

Detecting condition: 

Defective harness connector

Trouble symptom: 

Communication is impossible between electric brake booster control module and Subaru Select Monitor.

Wiring diagram: 

Electric brake booster system Ref. to WIRING SYSTEM>ELECTRIC BRAKE BOOSTER SYSTEM>WIRING DIAGRAM

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK IGNITION SWITCH  .

   Is the ignition switch ON?

   Yes  : Go to  2.

   No  : Turn the ignition switch to ON, and select the [Electric Brake Booster] using the Subaru Select Monitor.

2. CHECK BATTERY  .
   1. Turn the ignition switch to OFF.
   2. Measure the battery voltage.

   Is the voltage 11 V or more?

   Yes  : Go to  3.

   No  : Charge or replace the battery. Ref. to STARTING/CHARGING SYSTEMS (H4DOTC)>BATTERY

3. CHECK BATTERY TERMINAL  .

   Is there poor contact at battery terminal?

   Yes  : Replace or tighten the battery terminal.

   No  : Go to  4.

4. CHECK INSTALLATION OF ELECTRIC BRAKE BOOSTER CONTROL MODULE CONNECTOR  .

   Turn the ignition switch to OFF.

   Is the electric brake booster control module connector inserted into the electric brake booster control module until the clamp locks?

   Yes  : Go to  5.

   No  : Insert the electric brake booster control module connector into the VDC CONTROL MODULE & H/U.

5. CHECK LAN SYSTEM  .

   Check the LAN system. Ref. to LAN SYSTEM (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE

   Is the check result OK?

   Yes  : Go to  6.

   No  : Perform the diagnosis for LAN system.

6. CHECK SUBARU SELECT MONITOR COMMUNICATION  .
   1. Turn the ignition switch to ON.
   2. Check whether communication to the electric brake booster system can be executed normally.

   Is the [Select Function] screen displayed?

   Yes  : Check the DTC of the electric brake booster system. Ref. to ELECTRIC BRAKE BOOSTER (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) 

   No  : Go to  7.

7. CHECK SUBARU SELECT MONITOR COMMUNICATION  .

   Connect the Subaru Select Monitor to another vehicle to check whether the communication for initializing can be executed normally.

   Does the Subaru Select Monitor communicate normally?

   Yes  : Go to  8.

   No  : Repair or replace the Subaru Select Monitor.

8. CHECK POWER SUPPLY CIRCUIT  .
   1. Turn the ignition switch to ON. (Engine OFF)
   2. Measure the ignition power supply voltage between electric brake booster connector and chassis ground.

      Connector & terminal 

      (B80) No. 1 (+) - Chassis ground (-):

      (B80) No. 20 (+) - Chassis ground (-):

   Is the voltage 10 - 15 V?

   Yes  : Go to  9.

   No  : Repair the open circuit of harness between electric brake booster control module and battery.

9. CHECK HARNESS CONNECTOR BETWEEN ELECTRIC BRAKE BOOSTER CONTROL MODULE AND CHASSIS GROUND  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from the electric brake booster control module.
   3. Measure the resistance of harness between electric brake booster control module connector and chassis ground.

      Connector & terminal 

      (B80) No. 9 - Chassis ground:

   Is the resistance less than 10 Ω?

   Yes  : Go to  10.

   No  : Repair the open circuit of the electric brake booster control module ground circuit and poor contact of connector.

10. CHECK POOR CONTACT OF CONNECTOR  .

    Is there poor contact of control module power supply, ground circuit and data link connector?

    Yes  : Repair the connector.

    No  : Replace the electric brake booster control module. Ref. to BRAKE>BRAKE BOOSTER