Immobiliser

An immobiliser is an electronic security device fitted to a motor vehicle that prevents the engine from starting without the correct authentication. It is a common component of modern anti-theft systems and works by tying the ability to start the vehicle to a valid key or token rather than mechanical ignition alone.

Most immobilisers rely on a transponder embedded in the vehicle key or fob. When the key is used at the ignition or detected by a nearby reader, the immobiliser’s control unit exchanges a coded signal with the key. If the code is recognized, the engine management system is allowed to enable starting; otherwise, the system disables one or more essential functions such as the ignition or fuel supply, preventing the engine from starting.

Typical components include the transponder in the key, the immobiliser control unit, an interface to the engine control unit, a starter interrupt, and indicator lights. Passive immobilisers require no user action beyond possessing the correct key, while some active systems may involve periodic code challenges or integration with keyless entry.

Immobilisers are standard on many new vehicles and contribute to insurance ratings and theft deterrence. Advances in immobiliser technology include cryptographic authentication, rolling codes, and tighter integration with other security features. Older or aftermarket systems can vary in compatibility and effectiveness.

Security considerations acknowledge that while immobilisers reduce the risk of theft, no system is completely invulnerable. Criminal techniques attempting to bypass immobilisers exist, which is why manufacturers continually update designs. Keeping authorized keys secure and seeking service from authorized dealers for replacement or programming are recommended practices.