DTC U0073: Control Module Communication Bus Off

DTC detecting condition: 

• Data to be received via CAN communication do not arrive.
• A/C cooperation control does not operate.

Trouble symptom: 

A/C does not operate fully automatically.

1. CHECK LAN SYSTEM  .

   Check LAN system using the Subaru Select Monitor. Ref. to LAN SYSTEM (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE .

   Is the check result OK?

   Yes: Go to  2 .

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

2. CHECK A/C CONTROL MODULE  .
   1. Replace with a normally operating A/C control module.
   2. Read the DTC using Subaru Select Monitor. Ref. to HVAC SYSTEM (DIAGNOSTICS)>Read Diagnostic Trouble Code (DTC) .

   Is DTC U0073 displayed?

   Yes: Go to  3 .

   No: Replace the A/C control module. Ref. to HVAC SYSTEM (HEATER, VENTILATOR AND A/C)>CONTROL UNIT>REMOVAL .

3. CHECK CAN COMMUNICATION CIRCUIT  .

   Check the CAN communication circuit. Ref. to LAN SYSTEM (DIAGNOSTICS)>CAN COMMUNICATION CIRCUIT CHECK>LIST .

   Is the check result OK?

   Yes: It is possible that temporary poor communication occurs. Clear the memory. Ref. to HVAC SYSTEM (DIAGNOSTICS)>Clear Memory Mode .

   No: Repair or replace the CAN communication circuit.