Patent ID: 7280034

Claim:
An antitheft system for a vehicle configured to collate an ID code of an engine start key ( 5 A, 5 B) with an ID code recorded in an immobilizer control unit ( 17 ), and to allow the engine start key ( 5 A, 5 B) to start an engine when a result of a collation is affirmative, the system comprising: an allowance tool ( 5 C, 5 D) for allowing rewriting or writing of an ID code, the allowance tool being provided separately from the engine start key ( 5 A, 5 B), the allowance tool ( 5 C, 5 D) being incapable of starting an engine while the engine start key ( 5 A, 5 B) being incapable of allowing rewriting or writing of an ID code; and a start key registration function of collating an ID code of the allowance tool ( 5 C, 5 D) with the ID code recorded in the immobilizer control unit ( 17 ) without starting engine and without requiring any special manipulation with the key, and rendering an ID code of an engine key ( 5 ) corresponding to the ID code of the immobilizer control unit ( 17 ) when the result of the collation is affirmative, so that when the engine key ( 5 ) is inserted into a key cylinder ( 3 ), the inserted engine key ( 5 ) serves as the engine start key ( 5 A, 5 B).