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

DTC detecting condition: 

RAB CONTROL MODULE communication is shut down because of high speed CAN error.

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  .
   1. Start the engine.
   2. Using the Subaru Select Monitor, read all DTCs. Ref. to LAN SYSTEM (DIAGNOSTICS)>Diagnostic Trouble Code (DTC)>OPERATION .

   Is DTC U1073 displayed? (Current malfunction)

   Yes:  Go to  3.

   No:  It may be a temporary poor contact. Perform the 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)>Diagnostic Trouble Code (DTC)>LIST>CHECK USING THE DTC CHECK SHEET .
   2. Using the Subaru Select Monitor, read all DTCs. Ref. to LAN SYSTEM (DIAGNOSTICS)>Diagnostic Trouble Code (DTC)>OPERATION .

      DTC Check 

   Is DTC U1073 displayed? (Current malfunction)

   Yes:  Go to  5.

   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 all DTCs. Ref. to LAN SYSTEM (DIAGNOSTICS)>Diagnostic Trouble Code (DTC)>OPERATION .

      DTC Check 

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

   Yes:  Replace the control module.

   No:  Repeat step  5 until U1073 is not detected.