If starting the engine becomes impossible for some reason (drained electronic key battery, etc.), use the transponder built into the electronic key and perform the immobilizer authentication with the wireless access module. The immobilizer coil is built into the engine start/stop button. When the engine start/stop button is pressed, the immobilizer coil is energized through the wireless access module, and the immobilizer authentication is performed by placing the electronic key close to the engine start/stop button. If the wireless access module detects an electronic key whose electronic key ID is not programmed or cannot be authenticated, the DTC is set.