An abnormality determining section disconnects both a positive wire and a negative wire between a load module and a second ground circuit, connects one of a positive wire or a negative wire between a main power source apparatus and the second ground circuit, and determines whether there is an abnormality in a second main power source circuit based on an amount of power supplied to the second ground circuit in a state where one of the positive wire or the negative wire of the second main power source circuit is connected to a reference potential by the second ground circuit.