What is an immobiliser?

An immobiliser is a secondary line of defence alongside your key to keep thieves from starting your car. Immobilisers are hardwired into a car's wiring harness and, until deactivated, will cut power to the fuel pump or similar functions so the vehicle is completely impossible to start. Modern cars have both access and immobiliser control built into their key fobs, so unlocking the car with the key on you will deactivate the immobiliser. Older cars had their immobiliser controls on a separate fob from the car's key, usually with a dedicated port on the dashboard.