Patent attributes
A backup communication is automatically executed if a smart ID does not come back from a portable device though a comparison ECU transmits a smart ID request. In the backup communication, the comparison ECU transmits an immobilized ID request through a coil. The portable device receives the immobilized ID request if a user brings the portable device close to an engine start switch. The portable device transmits the immobilizer ID to comparison ECU. The comparison ECU sends the immobilizer ID to an ID box. The ID box compares the immobilizer ID sent from the comparison ECU with the ID stored therein. If the immobilizer ID corresponds to the stored ID, an engine ECU allows an engine start.