immobilisersystem

An immobiliser system, or immobiliser, is an electronic security device in motor vehicles designed to prevent the engine from starting unless the correct authentication is presented by a key or fob. By limiting the ability to start the engine, immobilisers help deter theft and unauthorized use.

Principle of operation: A transponder in the key or a proximity chip in a fob communicates with an immobiliser control unit in the vehicle. When the vehicle is switched off, the system is armed. On an ignition attempt, the engine control unit checks the received code against its stored data. If the code matches, the starting circuit is enabled; if not, ignition and/or fuel delivery are disabled, and the engine will not start.

Components and variants: Common components include the transponder-equipped key, an antenna or reader near the ignition, an immobiliser control module, and the engine control unit. Some systems are passive, activating automatically when the authenticated key is present, while others require a user action such as pressing a button to arm or disarm. Modern designs often employ encrypted, rolling-code authentication to resist cloning and replay attacks.

Security considerations: Immobilisers have substantially reduced vehicle theft in many regions. However, vulnerabilities exist, such as relay attacks that extend the key’s signal range or cloning of transponder data. Ongoing advances emphasize stronger cryptographic methods and improved anti-tamper measures.

Maintenance and impact: Immobilsers are generally maintenance-free but can fail if the transponder battery is depleted, the antenna or wiring is damaged, or the control unit malfunctions. In such cases, authorized service is required to reset or reprogram the system.