Patent ID: 7265953

Claim:
A fault location identification and judgment method for a power supply boost control device having a power supply relay, a boosting circuit, and a precharge circuit, comprising the steps of: judging whether or not said power supply relay has a turn-on fault or said precharge circuit has a turn-on fault based on the voltage on the upstream side of said boosting circuit in a state in which the unit power supply is turned on, said power supply relay and said precharge circuit are turned off, and voltage boosting by said boosting circuit is prohibited; when said power supply relay is judged not to have a turn-on fault, judging whether or not said precharge circuit has a turn-off fault or the boosting prohibit function of said boosting circuit is faulty based on the voltage on the upstream side and the voltage on the downstream side of said boosting circuit in a state in which said precharge circuit is turned on; and when said precharge circuit is judged not to have a turn-off fault, judging whether or not said power supply relay has a turn-off fault based on the voltage on the upstream side of said boosting circuit in a state in which said power supply relay is turned on.