DTC U01B0: Lost Communication With Battery Monitor Module: Notes

DTC detecting condition: 

Immediately at fault recognition

Failure detection pattern: 

• "Primary" (high-priority diagnosis)

Warning light/indicator light: 

• Malfunction indicator light

Wiring diagram: 

Engine Electrical System Ref. to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM>2.0 L MODEL .

Courtesy of SUBARU OF AMERICA, INC.

1. BASIC INSPECTION  .

   Before performing the diagnosis, perform basic inspection. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0)>GENERAL DESCRIPTION>INSPECTION .

   NOTE:

   • Check the battery and its installation condition.
   • Check the related fuse.
   • Visually check that the related connectors are properly connected.

     Also, check the related ground terminal for looseness and corrosion.

   Is the check result OK?

   Yes  : GO TO  2.

   No  : Repair the defective part.

   After the repair, GO TO  4.

2. CHECK HARNESS (OPEN CIRCUIT IN BATTERY SENSOR POWER SUPPLY LINE)  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from battery sensor.
      CAUTION: When disconnecting the connector, check for poor contact due to damage, looseness, adherence of foreign matter on the connector and terminal.
   3. Measure the resistance between the following terminals.

      Connector & terminal: Standard 

      Battery positive terminal - (B91) No. 1: Less than 1 Ω

      Battery positive terminal - (B91) No. 2: Less than 1 Ω

   Is the check result OK?

   Yes  : GO TO  3.

   No  : Repair the defective part.

   After the repair, GO TO  4.

3. CHECK HARNESS (OPEN CIRCUIT IN BATTERY SENSOR COMMUNICATION LINE)  .
   1. Disconnect the connector from ECM.
      CAUTION: When disconnecting the connector, check for poor contact due to damage, looseness, adherence of foreign matter on the connector and terminal.
   2. Measure the resistance between the following terminals.

      Connector & terminal: Standard 

      (B62) No. 17 - (B91) No. 3: Less than 1 Ω

   Is the check result OK?

   Yes  : Replace the battery sensor. Ref. to STARTING/CHARGING SYSTEMS (H4DO)>BATTERY SENSOR .

   After replacement, GO TO  4.

   No  : Repair the defective part.

   After the repair, GO TO  4.

4. CHECK REPAIR  .
   1. Perform the inspection mode corresponding to DTC. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0)>INSPECTION MODE>PROCEDURE .
   2. Confirm that DTC or cancel code is not stored and the malfunction is eliminated.

   Is the check result OK?

   Yes  : Finish the diagnosis.

   No  : Perform the diagnosis according to the basic diagnostic procedure. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .