The immobilizer is an electronic anti-theft device. It is activated when the ignition key is removed and, together with the engine control unit, largely prevents unauthorized starting of the engine. The system uses a transmitter and receiver unit in the ignition key (transponder). Whenever an attempt is made to start the engine, it transmits a new code to the car’s electronics. The immobilizing is only cancelled if the key sends an authorization code. New encryption technology protects the system against electronically copied vehicle keys.
No system can provide 100% protection against theft. If thieves possess the necessary skill and determination, they may even be able to overcome the electronic immobilizer.