DTC U0074: Control Module Communication Bus "Body-Can" Off

DTC detecting condition: 

Detected when malfunction occurs in CAN line. (Bus off)

Trouble symptom: 

In each screen, there are some items that are not displayed.

• Favorite screen is not properly displayed.
• Fuel economy screen is not properly displayed.
• Ambient air temperature is displayed in bar display.
• Only the advanced equipment screen, preventive safety screen, favorite screen, fuel economy screen, clock screen, and setting transition screen are displayed.

Wiring diagram: 

• Multi-function display (MFD) system Ref. to WIRING SYSTEM>Multi-function Display (MFD) System>WIRING DIAGRAM .
• CAN communication system Ref. to WIRING SYSTEM>CAN Communication System>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK DTC  .
   1. Using the Subaru Select Monitor, perform the clear memory of [Multi-Function Display]. Ref. to COMMON (diag)>CLEAR MEMORY .
   2. Turn the ignition switch to OFF.
   3. Disconnect the MFD connector and reconnect it.
   4. Turn the ignition switch to ON.
   5. Read the DTC of [Multi-Function Display] using the Subaru Select Monitor. Ref. to MULTI-FUNCTION DISPLAY (DIAGNOSTICS)>DIAGNOSTIC TROUBLE CODE (DTC) .

   Is DTC U0074 displayed? (Current malfunction)

   Yes  : Go to  2.

   No  : Even if DTC (past malfunction) is displayed, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

   NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.
2. CHECK HARNESS (GROUND SHORT CIRCUIT)  .
   1. Disconnect the MFD connector.
   2. Using a tester, measure the resistance between MFD connector and chassis ground.

      Connector & terminal 

      (i122) No. 19 - Chassis ground:

      (i122) No. 20 - Chassis ground:

   Is the resistance 10 kΩ or more?

   Yes  : Go to  3.

   No  : Even if DTC is displayed, the circuit has returned to a normal condition at this time. Reproduce the failure, and then perform the diagnosis again.

   NOTE: In this case, temporary poor contact of connector, temporary open or short circuit of harness may be the cause.
3. CHECK HARNESS (OPEN CIRCUIT)  .
   1. Disconnect the body integrated unit connector.
   2. Using a tester, measure the resistance between the MFD connector and body integrated unit connector.

      Connector & terminal 

      (i122) No. 19 - (B281) No. 17:

      (i122) No. 20 - (B281) No. 19:

   Is the resistance less than 10 Ω?

   Yes  : Go to  4.

   No  : Repair or replace the open circuit of harness.

4. CHECK LAN SYSTEM  .

   Perform the diagnosis for LAN system. Ref. to LAN SYSTEM (DIAGNOSTICS)>Basic Diagnostic Procedure>PROCEDURE .

   Is the check result OK?

   Yes  : Replace the MFD. Ref. to INSTRUMENTATION/DRIVER INFO>MULTI-FUNCTION DISPLAY (MFD) .

   No  : Perform the inspection according to the diagnosis for LAN system.