What is a car immobiliser & should I install an immobiliser in my fleet vehicles?

For those who don’t know, a car immobiliser is an electronic security device that will prevent your vehicle from being started without the correct key.
Immobilisers not only add extra security, but they can also help lower your car insurance premiums.
Here, we take a closer look at how they work, along with understanding the role of ghost immobilisers in modern vehicle security.
Car immobilisers – the basics
Put simply, a car immobiliser is an anti-theft device that enables your car to start only when the correct code that is sent from your key has been received.
It’s this technology that prevents a thief from bypassing the security system and stealing your car.
The key works with a transponder that is embedded in the fob, and it transmits a unique code to the car’s ECU ( Engine Control Unit ) when it is put into the ignition.
Years ago, car makers would have a button to be pressed to deactivate the immobiliser, or use a separate fob for this, or even have a keypad that needed a four-digit code – which the Citroen Xantia had.
The evolution of immobilisers
While having to key in a four-digit code to start the engine does sound like a faff, it was an effective deterrent.
Now, cars have keyless entry so the key needs to be close to the car to function.
Some cars also enable your smartphone to be used as a key.
Early immobilisers used a single code that was programmed into the system, but modern immobilisers use a different code each time you start the car.
This is where ghost immobilisers come into play.
Ghost immobilisers provide an additional layer of security by requiring a unique sequence of actions within the vehicle, such as button presses on the dashboard before the vehicle can start.
This sequence acts as a secondary immobiliser, making it even more difficult for thieves to steal the vehicle.
How do immobilisers work?
The main function of an immobiliser is to prevent the engine from starting.
Even when using the correct key, if the immobiliser does not receive the right code, it will not enable the engine to start.
Also, if a thief tries to ‘hotwire’ a car or bypass the immobiliser, including the ghost immobiliser, the car will not start because the starter motor – or the fuel system – will not respond.
Does my fleet car have an immobiliser?
Since 1998, it has been mandatory for all cars to have a factory-fitted immobiliser – though the technology has moved on from then.
If your car is older, it might still have an immobiliser fitted.
The first immobilisers that used a key with an embedded transponder arrived in 1992 – mainly by luxury carmakers who were quick to utilise the new technology.
Unfortunately, car thieves were also enthusiastic about this progress, and they too began developing ways to get around the new security measures.
If you are unsure of whether your vehicle has an immobiliser, check the owner’s manual or contact the manufacturer to find out.
I’ve got an old car – does it need an immobiliser?
Regardless of how old your car is, thieves may still want to steal it. Vintage cars and even old Land Rovers are hugely popular for their parts.
However, immobilisers are proven theft deterrents which makes them a wise investment for older vehicles lacking this technology.
Installation costs range from £200 to £500, with some companies offering on-site service.
Choosing a Thatcham-approved device (see below) ensures the system meets rigorous security standards.
Also, installing an immobiliser in an older car might lower your insurance premiums.
Car immobiliser options – understanding the security categories
While mandatory for new cars, immobilisers come in various forms.
Factory-fitted systems offer seamless integration, but you might want to add an aftermarket system.
If so, that means understanding the security effectiveness of the system, although navigating the security ratings can be tricky.
That’s where Thatcham Research, established in 1969, comes in because it sets independent benchmarks for car safety and security.
Their rigorous testing process evaluates immobilisers and alarm systems, so you’ll need to ensure you look for Thatcham-approved devices for guaranteed performance.
Here’s a breakdown of Thatcham’s car security categories:

Category 1: Integrated Alarm & Immobiliser: Offers perimeter detection, movement sensors, and immobilisation of critical systems.
Category 2: Electronic Immobiliser: Controls at least two vital vehicle functions to prevent starting.
Category 2/1: Upgraded Alarm: Enhances security for cars lacking a factory-fitted alarm, meeting Category 1 alarm criteria.
Category 3: Mechanical Immobiliser: Steering wheel locks or wheel clamps require manual activation for each parking session.
Category 4: Wheel Locks: Uses specialised tools to deter theft and serve as a visual deterrent.
Category S5: Post-Theft Tracking & Immobilisation: Enables stolen vehicle location, remote immobilisation, alerts authorities, and features driver identification for additional security.
Category S7: Stolen Vehicle Location: Similar to S5 but lacks driver recognition and remote immobilisation.
Q Class: Unrated Aftermarket Devices: These haven’t undergone Thatcham’s evaluation process.

By understanding these categories, you can choose the best immobiliser to safeguard your vehicle.
What else can I do to immobilise my fleet vehicle?
While having a car immobiliser will be a deterrent, for maximum protection you should employ a multi-pronged security strategy.
That means combining electronic and physical deterrents that will thwart not only tech-savvy thieves but the opportunistic ones as well.
You could consider adding electronic defenders such as:

Alarms: Produce a loud noise to scare off intruders
Trackers: Locate your stolen car for swift recovery – but having one fitted will put some thieves off
Remote immobilisation: Cut off the engine remotely, stopping thieves in their tracks
Driver identification: Restrict the car’s operation to authorised users – usually a tag that is separate from the key fob.

In addition, there’s a growing trend to add physical barriers, such as:

Steering wheel locks: Visually deter theft and physically impede driving with a lock that fits over the steering wheel
Wheel clamps: Fit a clamp to a wheel to prevent the car from being driven away
Gear locks: A simple device to lock the gear stick and hinder operation.

This layered approach to securing your car will make it a less appealing target to thieves.
Read more:
What is a car immobiliser & should I install an immobiliser in my fleet vehicles?