What is an immobiliser, do I have one, and how does it affect my insurance?

An engine immobiliser is a device that only allows your car to start by using the correct key or fob. This means it won't start if the wrong key is used and your car is protected against hot-wiring by would-be thieves.

A factory-fitted immobiliser is generally considered more desirable as it is assumed the device installed by the vehicle's manufacturer is more robust and fit for purpose.

Thatcham is an independent institution that rates car security and helps car insurance companies factor this into their price calculations. A Thatcham approved device is therefore more likely to lower the cost of your insurance.

Thatcham has 7 classes for car security. The closer to first-class you get the more robust your security is.

• Class 1. An electronic alarm and immobiliser. This is the most secure and complex system available. Class one alarms will run on their own battery supply and immobilisers have the ability to activate on their own.
• Class 2. Electronic immobiliser. This is the class one immobiliser without the alarm.
• Class 2/1. An electronic alarm upgrade where you already have an immobiliser. This doesn’t push you up to class one but is the closest you can get without a new car.
• Class 3. Mechanical immobiliser. The most common kind of class three feature is a steering wheel lock. Mechanical immobilisers must be fitted each time you want to secure the car.
• Class 4. Wheel locks. This is where your alloys have wheel-locking nuts on them which can only be removed with a special key making them harder to steal.
• Class 5. Post-theft tracking. If your car is stolen the system will track its position so the police can recover it. They will also have the ability to immobilise the car remotely.
• Class 6. This is a tracker much like class five except without the ability to remotely immobilise the car.
• Class 7. A more simplistic version of the class six tracker.

Security devices that aren’t Thatcham approved fall outside of these groups and are known as Q class devices.

Factory-fitted immobilisers have been a requirement on all cars made in the UK since October 1998. So, if your car was made after 1998 you will definitely have a factory-fitted immobiliser installed. Older cars, and cars imported from other countries - particularly outside of Europe and immobilisers have been standard in Europe since 1998 as well - may not have one. If you've got an older car or an imported car, you will need to check if it has one installed. Some may have been fitted at the factory and others may have had them installed later.

How to check if your car has an immobiliser

The easiest way to check is your car owner's handbook or ask at your next service or MOT.

The higher the level of security your car has the harder it will be to steal. This means that your car will be safer, and your premiums cheaper.

Thatcham also lists a number of devices that will make your car safer and lower your premiums. The best way to secure your vehicle is to keep it in a locked garage when you're not using it.

Immobilisers work by sending a signal to an electronic control unit (ECU) in your car. Sometimes it may be faulty meaning you will be unable to start your own car. This is often down to a flat battery in your key fob, so a simple battery change is likely to solve the problem. Sometimes fobs will have manual keys so using the key should work if your fob fails.

If you are still having problems, then it is best to contact the garage or dealership you got your car from. Faulty immobilisers are very rare and it is by far the best way to ensure the safety of your vehicle and lower the cost of your insurance premium.