Tire-pressure monitor system

A tire-pressure monitor system comprising:

• wheel sensors, each of which comprises a pneumatic sensor to detect a tire pressure and a transmitter to repeatedly transmit wheel information that is information including tire-pressure information representing the tire pressure detected by said pneumatic sensor and a unique sensor ID, as a radio signal, and is fixed to and disposed in each of wheels of a vehicle, and
• a vehicle body side device which comprises a receiver to receive the wheel information which said wheel sensors transmit respectively, an ID registration portion to register therein the sensor IDs of the wheel sensors used as targets for an air pressure monitor, and a reporting portion to report to a driver of said vehicle the tire-pressure information transmitted from the wheel sensor specified by the sensor ID registered in said ID registration portion, and is fixed to and disposed in a vehicle body, wherein:
• said vehicle body side device comprises:
• a time measuring means to measure an unreceived period that is a continuous time period in which the wheel information specified by said sensor ID is not received under a situation where the wheel information specified by said sensor ID should be transmitted, for every sensor IDs registered in said ID registration portion,
• a malfunction reporting means to report a malfunction to said driver of said vehicle when said unreceived period exceeds a first set time for any of the sensor IDs registered in said ID registration portion,
• a total time calculating means to calculate total unreceived period which is a sum total of the unreceived period for a specific number larger than 1 of said sensor IDs,
• a rewriting means to start a discrimination processing for distinguishing the sensor IDs of said wheel sensors respectively disposed in the wheels of the self-vehicle among many and unspecified sensor IDs received by said receiver when said total unreceived period exceeds a second set time which is shorter than a time period obtained by multiplying said specific number by said first set time, and to rewrite the sensor ID registered in said ID registration portion to the sensor ID distinguished by said discrimination processing.