DTC U1073 Control Module Communication Bus "Sonar-Can" Off: Trouble symptom

CAN communication is not normal.

1. CHECK CAN COMMUNICATION HARNESS. 

   Perform the basic diagnostic procedure to check for fault in CAN communication harness. Ref. to LAN SYSTEM (DIAGNOSTICS)>Basic Diagnostic Procedure .

   Was the basic diagnostic procedure performed up to step 7?

   • Yes  : Go to 2. 
   • No  : Perform the basic diagnostic procedure. Ref. to LAN SYSTEM (DIAGNOSTICS)>Basic Diagnostic Procedure .
2. CHECK DTC (CURRENT MALFUNCTION). 
   1. Start the engine.
   2. Using the Subaru Select Monitor, read DTC of CAN system. Ref. to LAN SYSTEM (DIAGNOSTICS)>Diagnostic Trouble Code (DTC) .

   Is U1073 a current malfunction?

   • Yes  : Go to 3. 
   • No  : It may be a temporary poor contact. Perform the clear memory. Ref. to LAN SYSTEM (DIAGNOSTICS)>Clear memory .
3. CHECK CAN COMMUNICATION CIRCUIT. 

   Check CAN communication circuit. Ref. to LAN SYSTEM (DIAGNOSTICS)>CAN Communication Circuit Check>PROCEDURE .

   Is CAN communication circuit faulty?

   • Yes  : Repair the faulty portion, following the diagnosis procedure.
   • No  : Go to 4. 
4. CHECK DTC. 
   1. Perform the inspection using the DTC check sheet. Ref. to LAN SYSTEM (DIAGNOSTICS)>List of Diagnostic Trouble Code (DTC)>LIST>CHECK USING THE DTC CHECK SHEET .
   2. Using the Subaru Select Monitor, read DTC of CAN system. Ref. to LAN SYSTEM (DIAGNOSTICS)>Diagnostic Trouble Code (DTC) .

   Is U1073 a current malfunction?

   • Yes  : Go to  4.
   • No  : System is normal.
5. CHECK CONTROL MODULE. 
   1. Turn the ignition switch to OFF.
   2. Disconnect the control modules other than body integrated unit in order.
      NOTE: When disconnecting ECM or VDC Control Module, connect resistance of 120 Ω between CAN Hi and CAN Lo as an alternative of end resistance.
   3. Turn the ignition switch to ON.
   4. Using the Subaru Select Monitor, read DTC of CAN system. Ref. to LAN SYSTEM (DIAGNOSTICS)>Diagnostic Trouble Code (DTC) .

   Is there any control module that U1073 is not detected as a current malfunction?

   • Yes  : Replace the control module.
   • No  : Repeat 1) - 4) in step 3 until U1073 is not detected.