What is an immobiliser & does my car have one?

If you’re looking to buy or sell a car, or you’re in the market for a new car insurance policy, the term ‘car immobiliser’ is likely to crop up in your research. But what exactly are car immobilisers? And how can you find out if your car has one? We’re here to explain what car immobilisers are, how to find them in your vehicle, and whether you should consider getting one fitted.


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What is an immobiliser?


An immobiliser is an electronic device that prevents a vehicle from starting unless the correct key or key fob is used. First used in 1992, factory-fitted immobilisers (those fitted during the manufacturing process) have been compulsory on all new vehicles in England and Wales since October 1998.

Factory-fitted immobilisers are often considered the best type as you can guarantee they’ll be fitted properly and are specific to the car model. When obtaining an insurance quote, the provider will ask if your car is equipped with a factory-fitted immobiliser.


Does my car have an immobiliser?


You can rest assured that your car has a factory-fitted immobiliser if it was manufactured after October 1998. However, if your car was made before that date and you want to check if it has an immobiliser, the easiest way to check is to contact your car’s manufacturer or consult your owner’s manual.

Alternatively, you can get your car checked out by a qualified mechanic, who should be able to tell you if it has an immobiliser or not.


How do immobilisers work?


When you start your car, the key or fob sends a code to the electronic code unit (ECU) that permits the engine to start. If a thief attempted to steal the car by using an incorrect key, the immobiliser would activate and prevent the ECU from receiving the code. As a result, the engine would fail to start.

Immobilisers typically work by disabling two of the three of the main components that allow the car to start (fuel system, starter motor, ignition). There are several immobiliser types too, some of which require a manual PIN code, while others require a touch key. Many modern immobilisers can be operated using smartphone apps via Bluetooth


Advantages of immobilisers


A standard car insurance question is: ‘Does your vehicle have an immobiliser or alarm?’ This is because these devices have a significant impact on a car’s security – and the more secure the car, the less likely it is to be stolen.

Therefore, if your car has an immobiliser, insurers may deem your vehicle to be at a lower risk of being stolen, which is likely to result in a lower insurance premium. However, it should be noted that insurance policies are calculated using a wide range of factors, and an immobiliser is not guaranteed to reduce your premium due to the influence of these other factors.


What type of immobiliser is best?


As mentioned, factory-fitted immobilisers are regarded as preferable because they’re fit for purpose and installed by the manufacturer. However, if your car is not fitted with an immobiliser as standard, you can always have one fitted by a professional. In these cases, it’s best to opt for a Thatcham-approved aftermarket device.

Thatcham-approved immobilisers

Thatcham Research is a not-for-profit organisation that certifies alarm systems, rates the security of new vehicles, and defines car insurance groups. Since its establishment in 1969, Thatcham has become an industry benchmark, and their immobilisers are put through rigorous tests for performance, functionality, and design before they achieve certification and are assigned a Thatcham category.

There are seven categories of Thatcham certification:

  • Thatcham category 1 - Combined alarm and immobiliser

    Category 1 devices are the most sophisticated immobilisers on the market. They feature perimeter and ignition detection, and incorporate movement, glass break and tilt sensors. A self-powered siren that activates if your car gets broken into completes the package.

    Immobilisers in this class are required to pass rigorous Thatcham Category 1 tests, while they also need to be passively set (no input needed from the driver), making them the most comprehensive Thatcham-approved security system.

  • Thatcham category 2 - Electronic immobiliser

    Category 2 is Thatcham’s immobiliser-only category – alarms are not awarded this certification. These systems are required to isolate at least two systems or one vehicle control unit that is needed for the car to run efficiently. Like category 1, these need to be passively set.

  • Thatcham category 2/1 - Alarm upgrade

    Devices are awarded this status if a category 2 vehicle is upgraded by retrofitting a category 1 alarm. Retrofitted alarms can also lower your insurance premiums.

  • Thatcham category 3 - Mechanical immobiliser

    Unlike the preceding categories, category 3 security systems are mechanical, not electric, which means that they are physical devices that disrupt the way a car operates.

    They are usually straightforward to set and unset and can be permanently or temporarily installed. Examples of category 3 devices are steering wheel locks and gear lever locks.

  • Thatcham Category 4 - Wheel locking devices

    Locking wheel nuts are robust, reliable devices that feature traceability, a secure replacement procedure, and provide resistance to attack.

    If you have a modern car with alloy wheels, it will benefit from a wheel locking device as they require a special key to remove the nuts, meaning it will be much more difficult for thieves to steal your wheels.

  • Thatcham category S5 - Post-theft tracking and recovery systems

    Replacing category 5, Thatcham category S5 systems can track a stolen vehicle and also immobilise it remotely by restricting the engine’s functionality.

  • Thatcham category S7 - Stolen vehicle location

    Introduced in 2019, Thatcham category S7 superseded the previous category 6 and 7 ratings. This new category features more affordable devices than those rated S5 but lack their robust security features (i.e. remote immobilisation is omitted).


Should I get a car immobiliser fitted?


The prevalence of sophisticated immobiliser systems in modern cars represent an effective deterrent to would-be thieves, with the most tangible benefit being a potential reduction in your annual premiums. Always remember that quality counts, so be sure to opt for a Thatcham-approved device if your vehicle does not have a factory-fitted device.


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