TIRE AIR PRESSURE SENSOR UNIT, TIRE AIR PRESSURE MONITORING SYSTEM, AND METHOD OF RECORDING SELF-IDENTIFICATION CODES FOR TIRE AIR PRESSURE SENSOR UNIT

A sensor unit body 10 of a tire pressure sensor unit 1 is provided with external signal-importing terminals 22 for rewriting data of self-identification code stored in a ROM 21, so that a complex operation of associating the self-identification code of the sensor unit with its mounting position in the vehicle is eliminated by rewriting the self-identification code of the sensor unit 1 after the replacement to be identical to the self-identification code of the sensor unit 1 before the replacement, when a tire wheel is replaced due to a breakdown of the tire unit or a replacement between a summer tire and a winter tire.