Vehicle immobilisers are electronic security devices used to prevent the engine from running unless the specific transponder car key is in the same vicinity. These devices are used to reduce the incidence of car theft, since the vehicle cannot be hot-wired to start even if the thieves have gained entrance to the vehicle’s interior.
The technology works as soon as the key is inserted into the ignition switch, or as the Smart Key fob is brought into the vehicle. The car’s engine will only start if the code in the transponder chip inside the Smart Key fob or key corresponds to the code in the vehicle immobiliser.
New car models are usually already equipped with factory immobilisers as anti-theft devices. Older vehicles can still get the same benefits with the installation of add-on immobilisers.
2 Main Types of Immobilisers
Touch Key Immobiliser
A coded key must be “touched” into a designated receptacle in the vehicle so that the alarm can be disarmed, triggering a go-signal for the engine to start.
A keyring or key fob is fitted with a small coded chip; the code in the transponder is read by the immobiliser when the key is placed into the ignition switch, disarming the alarm system.
Approved immobilisers are required to have at least 2 circuits – the low-voltage ignition circuit, and the fuel pump circuit. There are other immobiliser systems that work on intercepting the low-current starter motor circuit, which runs from the key switch to the relay.