Car immobiliser

How a thief fools the factory immobiliser

There is a small chip in the key. When you turn the key or press the start button, the car asks the chip who it is.

If the answer is not the one the car knows, the engine will not start.

So the thief works to make the car believe it has the right key:

1. A new key through the OBD port. The OBD port is the socket under the steering wheel where diagnostics are plugged in. A thief plugs into it and can program a new key. More about OBD theft
2. Keyless theft. A keyless key unlocks and starts the car while it is in your pocket. Thieves pick up your key’s signal and relay it to the car. More about keyless theft
3. The headlight attack. On some cars a thief sends a fake message that the key is genuine through the cables by the front light. More about the headlight attack

The immobiliser we fit also asks for your fob, code or phone. For your model we check which device and which way of connecting it give extra protection.

How you start the car with a code

The code is a sequence of presses on buttons the car already has, for example on the steering wheel or the window switch.

1. Switch on the ignition. The dashboard lights come on, but do not start the engine yet.
2. Press the buttons in your order.
3. Wait for the confirmation. The device confirms the code is correct, for example by flashing a light on the dashboard.
4. Start the engine.

After fitting

1. Keep the backup outside the car. Carry it with you, and you can note the backup code in your phone.
2. Do not tell anyone the unlocking code. Whoever knows the code can unlock the engine.
3. Switch off service mode after servicing. Check the protection on the spot the way we showed you.
4. If the fob has a replaceable battery, we show you which one it uses and how to replace it.

More about what an immobiliser is

Updated 25 October 2026.