Fault diagnosing apparatus for vehicle and fault diagnosing method for vehicle

摘要

A vehicle includes a direct current power supply, an electric circuit such as a DC/DC converter supplied with a current from the direct current power supply, a connecting portion that includes a plurality of relays and that connects and disconnects a path supplying the current from the direct current power supply to the electric circuit, and a voltage sensor monitoring the path between the connecting portion and the electric circuit. A control portion provides control to connect and disconnect the connecting portion. The control portion brings part of the plurality of relays into conduction to make a provisional determination of conduction fault of a relay that is to be non-conductive in accordance with an output of the sensing portion, and when a result of the provisional determination indicates fault, the control portion stores the output of the voltage sensor as a first value and provides control to once bring part of the relays out of conduction and bring the part of the relays into conduction, and thereafter compares the first value and the output of the voltage sensor to determine whether or not to confirm the provisional determination. Thus, a fault diagnosing apparatus and a fault diagnosing method which reduce a time for a fault diagnosis can be provided.