What type of alarm and/or immobiliser does your car have?

What is a car immobiliser?

There are lots of things to consider when buying or selling a car, or just applying for insurance, and one of those is a car immobiliser. But what exactly is a car immobiliser and why is it so important? 

What is a car immobiliser?

A car immobiliser is a clever bit of tech that stops your car from starting unless you are using the correct fob or key. Essentially, it’s the car equivalent of a home alarm system. Your key or hob serves as the pin number to de-activate the alarm, or in this case, activate the car. Without the correct key or hob, which gives the correct code to the engine, your car won’t be going anywhere. That means, as much as popular media may like to say otherwise, hotwiring a car isn’t actually possible in a lot of cases. 

This is all to do with the ECU, or electric control unit. While we may think of cars as very different to computers when it comes to tech, there’s more to a car than foot-down-and-go. A car also has its own computer, which is the ECU. This chip contains lots of key data including the commands for the power of the engine and its response time, as well as overall security. This is also why chipping your car can create such a big difference in performance. 

Does my car have an immobiliser?

While it seems like a security essential, it’s not actually a given that your car has an immobiliser. That said, it’s very likely that it does, given that all cars manufactured since October 1998 have one fitted as standard. Your vehicle’s handbook will be able to tell you for sure. Alternatively, an immobiliser may have been fitted by a previous owner. This won’t be outlined in the handbook, but a mechanic will be able to identify it for you next time your car is getting serviced.

How to find out what car alarm I have?

There are other security measures added to your car, the most obvious being the car alarm. If you aren’t sure what alarm you have, you should again refer to your owner’s manual. A mechanic can also help you. Of course, if it’s just a matter of knowing if it’s a silent alarm or not, you can just give your locked car door a tug and see if an alarm is set off.  

what is a car immobiliser
Car immobilisers and alarms help guard against vehicle theft.

Car alarm systems

These come in several types:

  • Silent alarms
  • Passive alarms that set automatically when you lock your car
  • Active alarms you have to set yourself
  • App-enabled alarms that function with GPS tracking

Even if your car has an immobiliser, it will likely still have a classic loud alarm that sounds when someone tries to get into your locked car. You can also have an immobilizer added on top of the alarm systems your car already has — insurance companies may even lower your premiums if you do.

Car immobiliser problems

While immobilisers are great security measures, there are some common issues that users may face, especially with immobilisers that were not fitted into the car at the point of manufacture:

  • Issues with locking
  • Probelms with engine starting
  • Issues with the car alarm activating 

Car immobiliser repair

Sometimes, just like a computer, resetting an immobiliser that is causing issues is a matter of turning it off and on again. Often, this can be done by holding down its activation button on your key fob. Key fobs can lose their power due to wear and tear and the internal batteries running low, but these aren’t hard to fix. If you aren’t confident in doing this as a DIY job, always head to a professional. You don’t want to accidentally damage the chip inside which allows your fob and your car to communicate.  

car immobiliser fob in car keys
The fob in your car keys communicates with the immobiliser fitted in your car.

Car immobiliser fitting

Immobiliser fitting is relatively straightforward, but it’s worth knowing all the car security options out there. Thatcham Research is a research centre and not-for-profit organisation that certifies the alarm and security systems used by cars.

Thatcham categoryDefinition 
Category 1Alarm and immobiliser combinations
Passively set
Detect window breaks
Tilt sensors
Perimeter detection
Ignition detection
Category 2Electronic immobiliser
Immobiliser only 
Passively set
Category 2/1Alarm upgrade
For cat 2 immobilisers with a retrofitted alarm
Category 3Mechanical immobiliser
Physical devices such as a wheel lock
Category 4Wheel locking devices
Locking wheel nuts fit this category
Category S5Tracking and recovering systems
GPS systems to track stolen cars
Remote immobilisers that prevent a stolen car from being driven
Category S7Stolen car location
As with S5 but without immobilising capabilities

Once you’ve decided on what sort of device you want, you should also be sure to check that it is Thatcham-approved. You should also look for verified professionals who will be able to correctly fit your chosen device. It’s not recommended that you attempt this yourself. 

Car immobilisers and car insurance

The better protected a car is, the less chance there is of being stolen, therefore the less risk there is of insurance needing to pay for any claims. In short, that means insurance companies are big fans of car immobilisers. Thatcham-approved devices are the preferred option for many insurers, so you may find your premiums lower a little more compared to a generic device. 

If your car doesn’t have an immobiliser at all, it’s well worth adding one not just for insurance purposes but for your own peace of mind. 

Selling your car?

We have lots of guides full of quality information on selling your car:

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