Theft prevention system for motor vehicles

摘要

For registering or updating the information of second identification codes (ID2) stored in a theft prevention apparatus (18) when the theft prevention apparatus (18) is replaced, a third identification code (ID3) sent from a third apparatus (24) which is mounted in a motor vehicle is checked against a third identification code (ID3) stored in the theft prevention apparatus (18), and must be identical thereto. Even if a third party prepares and installs an ignition key (14) and a theft prevention apparatus (18) of its own on the motor vehicle, the third identification code (ID3) is not verified, and hence the information of second identification codes (ID2) cannot be equalized.