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.

CAUTION: Before performing diagnosis, refer to "CAUTION" in "General Description". Ref. to MULTI-FUNCTION DISPLAYS (DIAGNOSTICS)>GENERAL DESCRIPTION>CAUTION .

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 MULTIFUNCTION 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.
CHECK HARNESS (GROUND SHORT CIRCUIT).
1. Disconnect the MFD connector.
2. Using a tester, measure the resistance between MFD connector and chassis ground.
  Connector and 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.
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 and 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.
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.