When the A/T is failed, have an interview with the user to gather precise information on the failure status. After that, perform on-board test to check if the failure is reproduced, and then start repair work. If the repair work is started on the assumption that the A/T is the failure cause from the beginning, the cause would not be investigated, and moreover, the secondary failure may be caused, resulting in a waste of repair time. Failures regarding the A/T are categorized as follows. 1.Poor adjustment, poor installation between the engine and body, and malfunction due to non-genuine device installation 2.Poor engine performance 3.Malfunction of the electronic control device 4.Malfunction of the A/T inside (hydraulic control system, etc.) 5.Others (oil leakage, damage, etc.)