DTC U01B0: Lost Communication With Battery Monitor Module: Notes

DTC detecting condition:

Immediately at fault recognition

CAUTION: Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>GENERAL DESCRIPTION>PREPARATION TOOL>HOW TO USE CHECK BOARD .

NOTE: After the faulty parts are repaired or replaced, perform the final check in Basic Diagnostic Procedure. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .

Wiring diagram:

Engine Electrical System Ref. to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

CHECK DTC .
1. Turn the ignition switch to ON.
2. Using the Subaru Select Monitor or a general scan tool, read the DTC of [Engine]. Ref. to COMMON (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .
Is DTC U01B0 displayed? (Current code)

Yes: Go to 2.

No: Finish the diagnosis.

NOTE: DTC may be stored due to temporary poor contact, noise, etc.
CHECK ECM CONNECTOR .
Check the connecting condition of ECM connector.

Is the ECM connector correctly connected?

Yes: Go to 3.

No: Connect the ECM connector correctly.
CHECK FUSE (M/B) .
1. Turn the ignition switch to OFF.
2. Remove and check the fuses No. 4 and No. 5. Ref. to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM .
Is the fuse blown out?

Yes: Repair the following item.
- Blown out of fuse
- Short circuit to ground in harness between M/B and battery sensor connector
No: Go to 4.
CHECK HARNESS BETWEEN BATTERY AND BATTERY SENSOR CONNECTOR (OPEN) .
1. Disconnect the ground terminal from battery sensor. Ref. to REPAIR CONTENTS>NOTE>BATTERY .
2. Disconnect the connector from battery sensor.
3. Disconnect the positive terminal of battery.
4. Measure the resistance of the harness between battery positive cable terminal and battery sensor connector.
  Connector & terminal
  
  Positive cable terminal - (B91) No. 1:
  
  Positive cable terminal - (B91) No. 2:
Is the resistance less than 1 Ω?

Yes: Go to 5.

No: Repair the open circuit in harness between battery positive cable terminal and battery sensor connector.
CHECK HARNESS BETWEEN ECM CONNECTOR AND BATTERY SENSOR CONNECTOR (OPEN) .
1. Disconnect the connector from ECM.
2. Measure the resistance of harness between ECM connector and battery sensor connector.
  Connector & terminal
  
  (B62) No. 17 - (B91) No. 3:
Is the resistance less than 1 Ω?

Yes: Repair the poor contact of ECM connector or battery sensor connector.

No: Repair the open circuit in harness between ECM connector and battery sensor connector.