What is an immobiliser and how can they affect car insurance?

What is a car immobiliser? And how do you know if you’ve got one? Here’s the lowdown on this clever piece of equipment – and how it might save you money on your car insurance.  

What is a car immobiliser? And how do you know if you’ve got one? Here’s the lowdown on this clever piece of equipment – and how it might save you money on your car insurance.  

Daniel Hutson
From the Motor team
minute read
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Posted 29 JANUARY 2020

How do immobilisers work?

An immobiliser works alongside your alarm to stop thieves from stealing your car. It’s part of your car’s security system, and with any luck you won’t ever see it in action. 
The exact mechanism of immobilisers is typically kept secret to stop thieves from disabling them. They basically stop your car from starting if someone tries to do so without the proper keys. If the wrong key is used or the car is hotwired, the immobiliser will be activated. When it detects that the code sent from the key doesn’t match that of the car’s electronic control unit (ECU), the immobiliser isolates some of your car’s components. Because of this, the ignition can’t start the engine. 
If you have an immobiliser, it could net you some savings on your insurance premium.  

What is a factory-fitted immobiliser – and do I have one?

A factory-fitted immobiliser is one that was installed when your car was made. These are often considered to be the best type, as they are likely to be fitted properly and suitable for the car.  
Your insurance provider will ask if there’s a factory-fitted immobiliser on board. But how can you tell? 

Factory-fitted immobilisers first started appearing in 1992. They have been compulsory on new vehicles in England and Wales since 1998. If your car was made after that date, it’s likely to have one, unless it’s been imported or a previous owner has removed it.  
It’s important to be sure, as you don’t want to risk problems with your insurance policy by suggesting your car has an immobiliser when it hasn’t. The simplest way to find out is to check with the manufacturer. You can do that by getting in touch directly or checking the car’s manual. Most car manufacturer’s websites will provide their contact details. If you still can’t find out, you can get a mechanic to check.  

What is a Thatcham-approved immobiliser? 

You may also be asked about ‘Thatcham approved security systems’ during your insurance quote. Thatcham Research is an organisation that certifies alarm systems, rates the security of new vehicles and defines car insurance groups
There are seven categories of Thatcham certification. The categories that insurance providers usually ask for are categories one and two. Category One is an electronic alarm and immobiliser, and Category Two is an electronic immobiliser without an alarm.  
There are also other Thatcham-approved security devices, including mechanical immobilisers, wheel locks and tracking systems.  
The Thatcham website has a complete list of Category One and Category Two approved, factory-fitted devices – listed in manufacturer order. You can also download the list as a PDF. 
If you’re interested in finding more out about how secure your car is, Thatcham has a research database where you can look up your car’s security rating. 

What if my car hasn’t got a factory-fitted immobiliser?

If your car hasn’t already got an immobiliser, you can get one fitted, but you need to make sure it’s Thatcham- approved and fitted correctly.  

Does an immobiliser count as a modification?

Fitting a vehicle immobiliser, or buying a car with an after-market immobiliser on board, may count as a modification for insurance purposes. But it depends on the insurance provider.  

Some modifications can negatively affect your car insurance, but for the majority of insurance providers, a security modification can be good news. There are no guarantees, however. That’s why it’s always best to double-check with your insurance provider. 

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