What is an immobilizer in a car and what is it for

One of the prerequisites for car insurance in some companies is the presence of an immobilizer in the car. Sometimes the owner of the car may not even know that this device is present in his car.

What is IMMO? What is its purpose and how does it work?

What is immobilizer

What is an immobilizer in a car and what is it for

This is an electronic system that prevents the engine from running, causing it to stall or not start. The immobilizer consists of several components:

  • key fob;
  • Control block;
  • electrical circuit breaker.

Depending on the modification of the device, it can be equipped with one or more trip relays.

All models are divided into several types.

  • Contact and non-contact. The deactivation code is read remotely, or with physical contact (for example, a fingerprint scanner).
  • Regular and additional. Some are installed at the factory, others at service stations.

What is an immobilizer for?

What is an immobilizer in a car and what is it for

Based on the translation from English, the purpose of the device is to immobilize the power unit. It is used as an additional element of the anti-theft system. The main task is to disconnect the electrical circuit in the ignition system and other components of the power unit.

Devices are equipped with breakers for starter, fuel pump or ignition coil. Depending on the modification, they can prevent the motor from starting or turn it off after a short period of time.

How the immobilizer works

What is an immobilizer in a car and what is it for

IMMO works according to the following principle: the car computer is configured to activate the power supply system of individual units in the presence of a command from the immobilizer.

The safety device control unit must obtain an access code from the vehicle owner. Depending on the model, this may be:

  • signal from the chip built into the ignition key;
  • key card located at an acceptable distance from the code reader;
  • a combination of symbols on the control panel;
  • owner's fingerprint.

These parameters are entered into the device software when it is configured. If the data received by the control unit and the initially set match, the machine's ECU receives a signal to start the engine. In the case of a standard IMMO modification, the control unit itself deactivates the blocking of the electrical circuit to which it is connected.

What happens if the immobilizer control unit receives an incorrect code? Here are the options (depending on modification):

  • the car's system power will turn on, but when the key is turned in the ignition lock, the engine will not start;
  • the electronic control unit of the car will receive a start signal, but as soon as the vehicle starts moving, the internal combustion engine will turn off;
  • The machine's ECU will start the engine, but after a while the device will give a signal to turn off the power.

What happens if you find where the immobilizer is installed and disconnect it from the system? The engine will still not start, since the anti-theft system control unit is synchronized with the car's ECU. The electronics of the car simply will not receive the right command, even if you try to start the car by closing the contacts in the ignition system.

The following video shows how to install this unit:

Do-it-yourself Immobilizer installation from Sergey Zaitsev

How to disable the immobilizer

Since the device does not just block the car door, but is built into a complex vehicle system, it is not so easy to disable it. Someone thinks that it is enough to cut the necessary wires and that's it. In fact, until the executing device receives the correct command, the machine will be locked.

This is the main advantage of immobilizers. If the wire is simply cut, the device interprets this as a hacking attempt, and goes into blocking mode or does not exit from it. Most models lock the car automatically, so it is dangerous to leave the car without a key.

You can turn off the immobilizer yourself, as opposed to connecting. There may be several reasons for this procedure. One of them is the loss of a key. Sometimes the control unit of the device fails, which can also be the reason for its shutdown.

Before considering how to turn off the immobilizer, it is worth remembering: each model has its own principle of operation, and at the same time a method of painless shutdown. If the procedure is not followed correctly, the electronics of the machine can be seriously damaged.

If the model provides for the entry of an access code, then if the key is lost, in order to deactivate the device, it will be enough to enter the corresponding code. If a new key is purchased, the immobilizer will need to be flashed again. If you have a spare key, you need to carefully remove the chip from its case and fix it near the immobilizer antenna.

What is an immobilizer in a car and what is it for

In the absence of a chip, you will have to purchase a special decoder. However, this is akin to hacking, which can be exploited by a hijacker, which is why auto protection manufacturers try to prevent such a circumvention.

The safest way to deactivate the immobilizer is to contact the device manufacturer (if emergency protection was installed) or to the car dealer (in the case of a standard immobilizer). This, of course, will require spending time and money, but dismantling or reinstalling the device.

If there is no desire to spend so much time and effort, then some motorists use a so-called emulator. The device bypasses the immobilizer protection and generates a shutdown signal, which is recognized by the control unit. However, the use of such devices is permitted solely at your own risk.

Immobilizer types

Today, manufacturers have produced many types of immobilizers, which expands the possibilities of use on different vehicles. Here are some of the features of each of them.

OEM immobilizers

This type of device is installed in the car on the conveyor belt. The vehicle electronics work with a corresponding signal from the protection control unit. Such immobilizers are extremely difficult to dismantle on your own without the appropriate skills and knowledge.

What is an immobilizer in a car and what is it for

The set of the device includes a power supply, an antenna and a key with a chip. The transponder itself, placed in the key body, does not need a battery, since the principle of operation is magnetic interaction. Most often, such devices do not break the electrical circuit in the car system, although there are models that break the circuit, for example, a starter (found in some models BMW).

Additional immobilizers

Any immobilizer that is not installed at the factory can be freely considered additional. Such a device is used as an additional anti-theft system.

The principle of blocking electrical circuits by immobilizers

Today there are two types of additional immobilizers, which differ in the principle of blocking car systems:

  • Contact immobilizers. These devices have a relay, which, with a corresponding signal, either connects or breaks the circuit in which the control unit is installed. This type of protection has proven itself in the anti-theft market. They can be triggered by a code that must be entered on the control panel or by a key signal.
  • Contactless immobilizers. In such systems, there is no wired connection between the actuator and the protection control unit. The signal is transmitted to them via Bluetooth.

Before installing contact modifications, it is worth clarifying how the car's electronics will react to signals from the control unit. Sometimes the ECU recognizes an open circuit as errors and requires them to be reset. In any case, the immobilizer must be selected for a specific car.

Code immobilizers

Devices of this type, in addition to the control unit and the actuator, have a keyboard for entering the previously set code. For such immobilizers, a key is not required, but does not protect from prying eyes.

What is an immobilizer in a car and what is it for

Some models have only one button. The code will be the time interval between clicks. The hijacker will have to mess around for a very long time, selecting the desired code. For this reason, such immobilizers are considered reliable. Even if a thief steals the car keys, he still won't be able to steal it.

Contact immobilizers

This type of protection includes devices that require a signal contact to unlock the machine. This can be a special key with a magnetic code or a fingerprint touchpad.

Immobilizers with contact key

Such immobilizers are the first protective devices of this type. A special key was brought to the control unit or to a special module in which the open contacts are located. The action closes the circuit and the vehicle can be started.

What is an immobilizer in a car and what is it for

Since such protection was very easy to bypass (it was enough to close the contacts in the block), manufacturers quickly modernized it and added it with a code key, which formed the signal required to close the circuit.

Immobilizers with Fingerprint Scanning

Instead of a module to which a special key is attached, the device is equipped with a contact surface that reads the car owner's fingerprint. Since the hijacker can force the car to be unlocked, the manufacturers equip the device with the so-called alarm fingerprint recognition function. When the system is activated in "emergency" mode, the engine starts, but after a while it stalls.

Contactless immobilizers

These devices include immobilizers, which can be activated / deactivated at a certain distance from the car, like an alarm. Distinguish between models with a large and short range.

What is an immobilizer in a car and what is it for

Short-range transponder immobilizers

Such systems have an antenna. It is installed under the dash panel as close to the body as possible. When a motorist brings a special key fob a few centimeters away, codes are exchanged using a magnetic transmission between the antenna of the translator and the chip itself.

Due to the fact that the key fob does not broadcast any signals, it is impossible to break the protection. Modern security systems have been modernized in such a way that with each separate pairing a new code is generated, synchronously generated by the key card and the control unit itself.

Long range immobilizers (with radio channel)

As the name of the device implies, the signal in them is transmitted over the radio channel and over a greater distance than in the previous modification. Basically, the range of the transmitter is about one and a half meters, and the communication channel is encrypted.

What is an immobilizer in a car and what is it for

Signals are exchanged in the "dynamic dialogue" mode, that is, a new code is constantly generated, which is recognized by the receiver as a master key. With increasing frequency, the range also increases. So, some protective systems are triggered at a distance of up to 15m.

If a similar system is installed in the car, then it is better to store the tag key not with the car keys. This will block the vehicle when the kidnappers took possession of the vehicle along with the driver, but threw it away on the way. Recent developments allow devices to be created that are so small that they can be easily hidden in the car's wiring.

Long range immobilizers with motion sensor

What is an immobilizer in a car and what is it for

Protection of this type allows you to leave the running car for a while without deactivating the engine. The advantage of this protection:

  • The thief stole the car, but after a while the engine simply stalls. In most cases, the thief will quickly leave the crime scene, leaving the vehicle behind.
  • If you need to leave a running car for a while (for example, while the interior is warming up in winter), without worrying that it will be stolen. Although a share of stress in such a situation is still present, since no one is pleased to find that the car is not standing still.
  • Immobilizers with a motion sensor allow you to remotely start the car engine (if the car has such a system).

The motion sensor determines the distance to which the key tag is removed from the receiver, as well as the rate of removal.

Which is better: immobilizer or alarm?

Although IMMO and the signaling are elements of the anti-theft system, each of them is installed for different purposes.

  • The signal is designed to prevent an intruder from entering the car. It protects against theft of valuable devices, such as a radio tape recorder, a video recorder or expensive things left in the car. In case of unauthorized access, she notifies those around about a hacking attempt.
  • The immobilizer prevents the thief from starting the engine and stealing the car. It does not warn the owner of the car about burglary attempts and does not protect against theft of items from the car.
What is an immobilizer in a car and what is it for

Considering these factors, it cannot be said which is better, because the alarm and IMMO are not interchangeable. Do not think that the presence of a blocking engine start is a reliable protection against theft. The thief can try to steal the car in other ways, for example, by breaking into and towing it to another location.

It should be noted that some types of alarms are equipped with their own immobilizer. Such an anti-theft system is more reliable than installing one of these devices. In this case, the control unit can be installed anywhere in the car, which will complicate the task for the thief.

How to replace the immobilizer

If the immobilizer elements are out of order (all or some one), then it may require replacement. The ideal option is to take the car to a specialist. In the case of such protection, sometimes it helps to install a similar device instead of something that has failed. However, you need to know exactly where each component of the device is.

What is an immobilizer in a car and what is it for

It is worth considering that many immobilizers have several modules located in the most inaccessible places, which only specialists or dealers know about. This is done specifically so that the stolen vehicle cannot be simply unlocked. Each module only recognizes the signal for which the master is programmed.

If the control unit is changed, the system will need to be reflashed in order for the actuators to recognize the signals from the new device. In the case of standard modifications, the car's ECU will need to be reflashed. And this work should always be trusted by professionals.

Advantages and disadvantages of the immobilizer

What is an immobilizer in a car and what is it for

The anti-theft system is important for the safety of the vehicle. The more difficult it is, the higher its reliability. What are the advantages of the IMMO installation?

  1. To steal a car, the thief will need additional funds, for example, another towing vehicle or a special device for reading the key card code.
  2. It's easy to use. In most cases, the motorist does not need to perform any special manipulations to deactivate the lock at all.
  3. Even if the power is turned off, the car will still not start.
  4. It is impossible to immediately understand that this system is installed in the vehicle (it works silently).

Despite its high reliability, this device has a significant drawback. If a key card or a key fob with a chip is used, the thief only needs to steal them and the car has a new owner. If you lose the key, you can use a spare one (most devices are equipped with two copies). But this must be done in order to take the car to a service station for flashing the control unit. Otherwise, the attacker will use the access to the machine for his own purposes.

The following video exposes 10 common immobilizer myths:

TOP 10 misconceptions about immobilizer, chip keys, etc.


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