To detect opening/closing of a neutral detection hydraulic switch by a detection apparatus and detect breakage of a wiring line connected between the detection apparatus and the switch. Since a second contact and an ECU are connected to each other by two wiring lines, even if one of the wiring lines is broken, opening/closing of the neutral detection hydraulic switch can be detected through the remaining one of the wiring lines. Since different voltages are applied to the wiring lines through resistance type voltage dividing circuits, the occurrence of the wire breakage can be detected making use of the fact that the voltage detected by the ECU upon opening of the neutral detection hydraulic switch when one of the wiring lines is broken is different from the voltage when none of the wiring lines is broken.