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

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Have you ever compared car insurance online and been stumped by the question: does your vehicle have a factory-fitted immobiliser?

I’ll admit to having had no idea whether or not my last car had one, and always answered ‘no’ to hedge my bets – better to say you don’t have one and find out you’re wrong than to say you’ve got one only to find you don’t, I reasoned.

After all, saying you’ve got one might attract a premium discount, so you don’t want to diddle the insurer. Your car insurance will be cheaper if you have a factory-fitted immobiliser because your vehicle will be more secure against thieves.

And as it’s been factory-fitted, the insurer will be confident that it’s up to spec and properly installed. If you’re not sure what an immobiliser is, or whether or not you have one, read on and I’ll explain.

What is an immobiliser?

An immobiliser is an electronic security device which stops a vehicle from being started unless the correct digital key or token is present.

In other words, the car can only be started with its key, and hotwiring it would be no use.

On a mechanical level, immobilisers work by disabling at least two of the three main components which make your vehicle move, namely the ignition, fuel system and starter motor.

Disabling two of these things will prevent a vehicle from starting. When you put your key in the ignition, a code is sent from a transponder in the key itself to the vehicle’s electronic control unit (ECU), often via a receiver in the steering column.

The method will vary from one manufacturer to another, but they all work on the premise that the vehicle will only start if the key’s code matches that of the ECU.

The inner-workings of these devices understandably aren’t widely publicised as this would give thieves the chance to get the upper hand.

Do I have one?

Factory-fitted immobilisers have been mandatory on all new cars since 1998, so if your car was built after then, it’ll almost definitely have one – unless a previous owner has done some tinkering with it and disabled or removed it.

There may be some pre-1998 vehicles with factory-fitted immobilisers, but you’ll have to check your owner’s manual to be sure. Also, some older vehicles may have had an immobiliser retrofitted after they’ve left the factory.

Are all immobilisers the same?

Their function is the broadly the same, and their mechanisms may vary, but they’re organised into categories, with some immobilisers rated as more secure than others.

The Thatcham Motor Insurance Repair Research Centre is a not-for-profit research organisation concerned with safety and security equipment in the automotive industry.

You may have seen or heard the phrase Thatcham-approved alarm, or immobiliser, for example. You can see how Thatcham rates your car’s security here

Is it worth having one?

Having a factory-fitted, Thatcham-approved immobiliser will make your car more secure than a car without one. This should be reflected in cheaper car insurance premiums.

If your car doesn’t have one and you’re thinking of installing one, you should make sure it’s a Thatcham-approved device.

But an immobiliser isn’t your only security option, as there are other Thatcham-approved devices you can install to keep thieves at bay while lowering your premiums.

Thatcham-approved steering wheel locks, for example, may be a cheaper option. Of course the best way to secure your vehicle is to keep it in a locked garage, if possible, when you’re not using it.

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