What is an immobiliser and does it affect my car insurance?

Do you have a car immobiliser? We explain how to find out and why this clever piece of equipment could save you money on your car insurance.

Do you have a car immobiliser? We explain how to find out and why this clever piece of equipment could save you money on your car insurance.

Daniel Hutson
Motor insurance expert
5
minute read
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Posted 29 JANUARY 2020 Last Updated 24 MARCH 2022

How do immobilisers work?

An immobiliser is part of your car’s security system and works alongside your car alarm to prevent thieves from stealing your vehicle. 

There are two kinds of immobiliser: 

  • Mechanical immobilisers, such as steering wheel locks and gear clamps.
  • Built-in electrical immobilisers, which we’ll be focusing on in this article. 

Electrical immobilisers stop your car from starting if someone tries to hotwire it or uses the wrong key or key fob. The precise workings are usually kept secret to make it harder for thieves to disable them. Basically, if the code sent from the key doesn’t match that of the car’s electronic control unit (ECU), the immobiliser disables two or three key components of your car, namely the fuel system, start motor and ignition. It also triggers the car alarm. 

Most immobilisers today work passively, which means you don’t have to set them manually. This means there’s no risk of you forgetting to turn them on, but it does make it harder to tell if you have an immobiliser installed.

Does an immobiliser or alarm affect my car insurance?

Because they can reduce the risk of your car being stolen, having an immobiliser and car alarm could also cut the cost of your car insurance, depending on your insurance provider.

Your car may already be fitted with an immobiliser. If it’s not, you can have one fitted.

What is a factory-fitted immobiliser?

Factory-fitted immobilisers are installed when the car is made. They’re often considered to be the most effective, as they’re likely to be fitted properly and are suited to your car.

Do I have a factory-fitted immobiliser? 

Your insurance provider will ask if there’s a factory-fitted immobiliser on board. It’s important to know as it could affect your premiums. 

Factory-fitted immobilisers have been compulsory for new vehicles in England and Wales since 1998. If your car was manufactured after that date, it’s likely to have one, unless it’s been imported or a previous owner removed it.

The simplest way to find out if you have a factory-fitted immobiliser is to check your car manual or get in touch directly with the manufacturer. Most car manufacturer’s websites will provide their contact details. If you still can’t find an answer, a mechanic will be able to tell you.

What is a Thatcham-approved immobiliser? 

You might also be asked about ‘Thatcham-approved security systems’ when you’re looking for car insurance. Thatcham Research is an organisation that certifies alarm systems, rates the security of new vehicles and defines car insurance groups. Its certifications for alarms and immobilisers have become an industry benchmark.

You can search for approved security devices on the Thatcham website. This also includes mechanical immobilisers and tracking systems.

What’s the difference between Thatcham Category 1 and Category 2?

There are seven categories (or classes) of Thatcham certification. The lower the number, the more security that device offers. Insurance providers usually ask for Categories 1 and 2.

  • Category 1 includes an electronic alarm and immobiliser. It’s the most secure system available.
  • Category 2 includes an electronic immobiliser without an alarm. 

There’s also a Category 2-1, which involves installing a Thatcham assessed 2-1 alarm when you have a Category 2 immobiliser already in place. This gives your car Category 1 status.

Does my car have a Thatcham-approved Category 2 alarm?

Not all models have a Thatcham-approved alarm fitted as standard. To find out, check your car manual or get in touch with the manufacturer. 

If you want to install an alarm, always choose a Thatcham-approved model because it’s another way to potentially save on your insurance policy.

Are immobilisers effective?

Electrical devices can never be 100% foolproof. Sophisticated criminals tend to rise to the challenge of new technology, and keyless car theft is a possibility through what’s known as a relay attack. This uses electronics to extend your key’s signal making the car’s technology think the key is nearby.

Electrical faults can also occur, causing problems with locking/unlocking, engine starting and keys not working. You may just need to change the battery in your key fob, but if problems persist, get in touch with the garage or dealership that sold you the car. 

Generally speaking, issues are rare and immobilisers are considered effective anti-theft devices, particularly when you combine them with other sensible precautions.

These additional security measures could include: 

  • Parking your car in a garage or a secure, well-lit location, ideally with CCTV.
  • Not leaving valuables visible inside your car.
  • Making sure your car is properly locked when you leave it.
  • Storing car keys away from windows and front doors where they might be in plain sight.
  • Keeping your key fob in a faraday pouch to prevent thieves intercepting the signal.
  • Deactivating your key fob at night – check your car manual to find out if this is possible for your particular model.
  • Testing your car alarm regularly.

There’s more about securing your car in our article on how to prevent keyless car theft.

Frequently asked questions

Does an immobiliser count as a modification?

Any changes to your car that mean it no longer matches the manufacturer’s original specifications are known as modifications.

Factory-fitted immobilisers are part of this original spec, but if you fit an immobiliser or buy a car with an after-market immobiliser on board, it might count as a modification depending on your insurance provider. If this is the case, you’ll need to think about modified car insurance. The good news is that by making your car more secure, you’re likely to save money on your premiums.

Can I fit an immobiliser into an older car – and will it impact my insurance?

If your car hasn’t already got an immobiliser, you can get one installed, but you need to make sure it’s Thatcham-approved and fitted correctly. This’ll give you the best chance of reducing the cost of your car insurance.

How can I check my immobiliser works?

Putting your key in the ignition sends a code from the key to your car’s electronic control unit (ECU), which has a matching code. This will start your car. If you try to use the wrong key or don’t have the key at all, the immobiliser will stop the engine running. It will also trigger the car alarm.

Are there other security devices that work alongside an immobiliser?

Extra security will make your car harder to steal. That’s usually a good thing from your insurance provider’s point of view. 

Most cars have an audible car alarm included as standard. But while this may deter a car thief, it often gets ignored due to the high number of false alarms.

Silent alarm systems are another option. There’s no noise, but you’ll get an alert if someone tries to break into your car. Never try to intervene if this happens. Call the police and stay away from any potential danger.

You might also want to install GPS tracking. It won’t stop your car being stolen, but by showing where your vehicle is in real time, it makes it easier for the police to find it.

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