What is an immobiliser, how is it built and how does it work?


One of the most popular anti-theft devices installed in cars is the immobiliser. Currently, each vehicle destined for the European market is fitted with such a solution. Here, we check how the immobiliser works and whether it is effective in preventing cars from being stolen.

Car manufacturers are installing increasingly advanced anti-theft devices in the vehicles they produce. Immobilisers are no longer a novelty, but a norm. Their today’s popularity results from two factors: first, they are automatic (the user does not need to remember to activate them); second, according to research published in the Economic Journal, the common use of immobilisers has decreased the number of stolen vehicles by 40%.

What is an immobiliser, how is it built and how does it work?

An immobiliser is an electronic anti-theft device used in mechanical vehicles. It prevents the engine from starting.

This effect can be achieved in a number of ways, e.g. by blocking engine ignition or the computer controlling the work of the ignition system. An immobiliser is not a complex device and consists of two elements:

  • transponder – depending on the production year of the vehicle, it can come in the form of a remote control (then, it needs to be brought close to the steering column) or can be integrated in the car key or a card;
  • central unit or engine controller – they are fitted inside the vehicle.

How does an immobiliser work?

In order to unlock the engine, the driver needs to put the key in the ignition, after which signals are exchanged. Simply put, it works as follows: first, an electromagnetic field induces voltage in the system of the transponder (key), which transmits a unique code. This code is received and checked by the engine control module. Then, the controller emits its own code, received by the transponder, in order to verify the key. Yet another exchange of code signals takes place. If the engine controller recognises the key and if the codes are compatible, the locks are deactivated and the engine starts.

Car manufacturers use various forms of locks. The most common ones involve cutting off power from the fuel pump. A less common solution is to cut off the entire electronics.

Although the functioning of an immobiliser may appear complicated, in practice it only takes a fraction of a second to compare the signals. This means that this process is imperceptible to the driver. What happens when signals sent by the transponder and the central unit do not match and consequently the verification process fails? Depending on the solutions used by the manufacturer, when the codes are incompatible, the engine cannot be started or it will be turned off after a short while.

What kinds of immobilisers are there?

Immobilisers can be divided into factory fitted (installed in vehicles directly by the manufacturer) and additional (installed at customer’s request). A different division is made based on how the deactivation code is read. Here, the division is as follows:

  • touch immobilisers – the code is read after a physical contact, e.g. it is necessary to press a finger on a fingerprint scanner;
  • contactless immobilisers – the code is read from an electronic circuit integrated in the key (card).
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The owners of older Citroën cars may remember code immobilisers. These cars were unique for a keyboard installed inside the vehicle, which the driver used to enter a code. Today, this kind of immobilisers is no longer in use, as it has been replaced by immobilisers installed in the key fob (card).

It is worth knowing that regardless of the immobiliser kind, the removal of the central unit (which is not that easy to find in the vehicle) will not allow starting the engine. A lack of the correct signal will lead to an automatic engine lock. The reason is that the on-board computer interprets the lack of a signal from the central unit as information that the car is being started by a person unauthorised to drive the vehicle.

Interestingly, immobilisers are not used only in cars, but also in motorcycles. In the 1990s, Honda was the first manufacturer of motorcycles to start installing immobilisers in its vehicles.

Damaged immobiliser: most common symptoms?

Fitting a car with an immobiliser provides the driver with an additional anti-theft measure. In order for a thief to be able to drive away in such car, they will have to deal with the security device, which is not easy, although possible.

If the immobiliser is damaged, the driver will have difficulty starting the engine. Then, the engine will start and turn off after a second or two, or there will be no ignition at all. At the same time, the immobiliser warning light will light up or flash. Since usually it is the transponder inside the key fob (card) that gets damaged, specialists recommend using a spare key (card). If it works, i.e. the vehicle starts, it will still be necessary to visit the service workshop.

There are a number of potential causes of immobiliser failure. The most common include: damage to controllers or induction loops (which read the signal from the transmitter); torn immobiliser coil; or lack of correct synchronisation of keys.

Transponder failure is less inconvenient, as the driver can try using a spare key (card). Making an extra copy of the key, however, may be quite expensive. Service workshop staff have access to specialist software and devices to programme a new key (card). When choosing a service workshop, it is worth looking into their price lists: the price for such a service can be especially high in authorised workshops.

Fearing the high costs of repairing the immobiliser, some drivers remove the transponder from the key fob (card) and then install it permanently inside the car. This solution, however, is not ideal, since this way the driver loses an anti-theft security measure.

If the central unit is damaged, the driver is usually forced to tow the vehicle to a trusted service workshop. However, specialists are not always able to get rid of the problem on the spot: sometimes, the central unit is cleverly hidden or integrated with the engine controller, which means more work and higher costs.

How much does it cost to repair a damaged immobiliser?

The costs of repair of an immobiliser depend on many factors, including most of all the part of the immobiliser that is broken. If it is the transponder that is damaged, which is the most common fault, then the repair cost may be as high as PLN 1,000. That is how much you need to pay at an authorised service workshop for removing the damaged key (card) from immobiliser’s memory and uploading a new one. For more affordable prices, drivers can choose to have the damaged element repaired by a specialist from a smaller service workshop.

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In case the central unit gets damaged, the car owners should expect quite high costs. Specialists will not only have to locate the central unit, but also replace it. It is not always possible outside authorised service workshops. If a driver suspecting a central unit failure does not have a roadside assistance insurance, then they will have to additionally pay from their own pocket for towing the car. If the nearest authorised service workshop is located many kilometres away from where the car broke down, the bill can be high.

Does an immobiliser offer a 100% protection against car-theft?

No anti-theft security device is 100% sure – each has its own advantages and disadvantages. An immobiliser, however, may effectively scare a thief away. It needs to be remembered that the longer it takes to start a car, the higher the chance that the thief abandons the theft out of fear of being caught red-handed. According to specialists, what may successfully deter thieves are non-serial security devices, e.g. a steering wheel bar lock or a gearbox pin lock. Why?

As cars are fitted with advanced anti-theft devices, car thieves are abandoning lock picks in favour of jammer-type solutions (electronic devices blocking the key’s signal). In other words, they are not prepared for dealing with safety devices that have not been in use for a few years now. A steering wheel lock in the form of a metal bar, which is very rarely seen today, may effectively deter a car thief.

It is worth noting here that the immobiliser is not the only anti-theft device fitted in cars. Other popular solutions preventing theft include car alarm, gearbox pin lock and GPS trackers. Using two (or more) security measures increases the probability of a failed car theft.

Why is it worth buying full cover and roadside assistance package on top of an immobiliser fitted in a car?

Nowadays, each car leaving the factory is fitted with an immobiliser: an anti-theft solution that has become a standard. Unfortunately, it does not always deter car thieves. Since no anti-theft device offers 100% protection, the owners of especially expensive vehicles should consider buying a full cover insurance policy; whereas in case of an immobiliser failure, a roadside assistance cover may prove useful.

In order to minimise the risk of car theft, countries have begun to make it obligatory for car manufacturers to install immobilisers. For instance, since 1998, this solution has been obligatory for new cars offered in Germany, the UK and Finland. Much later, because only in 2007, the same requirement was introduced by Canada.

Full cover insurance is a product from the category of voluntary (additional) vehicle insurance. It guarantees a payment of compensation in case of a car theft, among others. How much does full cover insurance cost?

The price of full cover insurance depends on multiple factors, including most of all the value, make and model of the car as well as the insurance history of the driver. In the case of full cover, insurance companies also inquire about anti-theft devices installed in the car. In order for an insurance company to present an offer, it is necessary to declare at least one safety device.

Not only the owners of new vehicles should consider buying additional insurance policies. The older the car, the higher the risk of a failure. Especially those drivers who are afraid of a failure (including immobiliser failure) and often travel on longer routes should consider buying roadside assistance insurance. It guarantees the insurer’s help in case of random events. Under this policy, the insured parties are provided with e.g. towing services.

Source: insurance comparison site rankomat


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