The maintenance part of the CAN Bus Networks failure is very difficult due to the difficulty of the inspection and the variety of the cause of the failure. In this study, first, diagnosis process is classified into diagnosis process of non-communication in total and diagnostic process of partial communication failure. Second, based on the past fault code, we analyze the fault by analyzing the nearest fault by analyzing the faults through the array and diagram. And, if the past failure codes can not be analyzed, the CAN logger is used to collect data. After that, it is confirmed that the fault diagnosis can be performed effectively by analyzing and checking it. Through this, troubleshooting by the diagnostic process is suggested and the direction of troubleshooting that the field technicians can use for diagnosis and inspection of CAN Bus Networks is presented.