<p>The anti-theft device (2) has a data line (1) coupling it to an engine operating control (3), for inhibiting or releasing the operation of the engine. An external device (4) can be coupled to the data line, for exchange of data with the anti-theft device and/or the engine operating control. Pref. an electrical line which is already installed in the vehicle is used as the data line, the external device only permitted free exchange of data with the anti-theft device and/or the engine control device after a verification check is performed.</p>