IMMO0 (1)
Auto Terms,  Tips for motorists,  Blog,  Car device,  Machine operation

What is an immobilizer in a car and why is it needed

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 realize that this device is present in his car.

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

What is an immobilizer

IMMO1 (1)

This is an electronic system that prevents the engine from running, which is why it stalls or does not start. The immobilizer consists of several components:

  • keychain;
  • Control block;
  • 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 upon physical contact (for example, a fingerprint scanner).
  • Established and optional. Some are installed at the factory, others - at service stations.

What is an immobilizer for?

IMMO2 (1)

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.

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

The principle of operation of the immobilizer

IMMO3 (1)

IMMO works according to the following principle: the car computer is configured to activate the power supply system of individual nodes if there is a command from the immobilizer.

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

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

These parameters are entered into the device software when it is configured. If the data received by the control unit and the initial set match, the machine 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 possible options (depending on version):

  • the car’s system power will turn on, but when the key is turned in the ignition, 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 engine will turn off;
  • The machine ECU will start the engine, but after a while the device will signal to turn off the power.

What will happen if you find where the immobilizer is installed and disconnect it from the system? The motor still will not start, since the anti-theft system control unit is synchronized with the car ECU. The car’s electronics simply won’t get 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 device:

Installation of the Immobilizer with Your Hands by Sergey Zaitsev

What is the immobilizer made of?

The key element of the immobilizer is its ECU ("brains"), which are programmed separately from the standard electronic control unit, which is responsible for processing signals from all transport systems. The immobilizer ECU is based on a microcircuit programmed for certain algorithms.

In addition to these algorithms (they activate a certain protection against theft - different devices have their own), the microprocessor firmware also contains an exchange code. This setting allows the device to recognize the car key when it is within range of the receiver. Information from the key is read using a special coil located in the same control unit.

The second element of the immobilizer is blockers. Electromagnetic relays are included in the design of each actuator. They are installed in the gap between different electrical circuits of the car, starting from turning on the ignition and ending with unlocking the brake system. It all depends on the model of the device and its installation.

What is an immobilizer in a car and why is it needed

An electrical signal from the control unit is sent to each switching device, due to which the circuit in the system is either broken or, on the contrary, connected. Some modifications of the blockers provide the ability to control the performance of non-electric mechanisms.

The third important element of any immobilizer is the transponder. This is a programmed chip that fits into the body of the car key. The code transmitted by the transponder is unique, and the microprocessor of the control unit is programmed for it. If there is a key from another car in the range of the receiver, the ECU will not send commands to the actuators, since this transponder is broadcasting an inappropriate signal.

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 performed 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 why is it needed

 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 manufacturer of the device (if an emergency protection was installed) or to the car dealer (in the case of a standard immobilizer). This, of course, will need to spend 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. 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 why is it needed

The set of the device includes a power supply, 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 BMW models).

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 the vehicle systems:

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 why is it needed

Some models have only one button. The code in this case 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. Action closes the circuit and the vehicle can be started.

What is an immobilizer in a car and why is it needed

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 necessary 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 why is it needed

Short-range transponder immobilizers

Such systems have an antenna. It is installed under the dash panel as close as possible to the body. 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 why is it needed

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. Thus, 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 wiring.

Long range immobilizers with motion sensor

What is an immobilizer in a car and why is it needed

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

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

How the immobilizer is controlled

Remote control of different immobilizer options depends on the type of device and the car on which such protection is installed. The car owner has several ways to control the immobilizer.

Label management

A tag refers to a small key fob that should be kept separate from the car keys. When the tag is in the range of the immobilizer signal, the protection will unblock the ability to start the engine. While this key fob is in the passenger compartment or near the car, the immobilizer is disabled.

The main thing when using the tag is to keep an eye on the battery. If it is discharged, the immobilizer will not recognize the tag, since it does not broadcast a signal. Of the varieties of tags, there are devices that operate on a radio signal or transmit a signal via Bluetooth. In the second case, the key fob can be configured for the range of communication with the immobilizer, the length of the pause between the detection of the tag and the removal of protection.

Smartphone control

In models working via Bluetooth, there is a function of working through a mobile application. In this case, the smartphone can be used as a tag. The phone or Apple Watch, through the turned on application via the bluetooth channel, broadcasts a signal and synchronizes with the immobilizer

What is an immobilizer in a car and why is it needed

The application should work all the time until you need to put the car on the lock. Accordingly, if the phone is located further than the signal range, the immobilizer initiates blocking, protecting the car from theft.

Control of buttons in the car (secret or coded immobilizer)

If an immobilizer with a digital connection (via a CAN connector) is installed in the car, then the lock is put on / off by pressing a combination of buttons in the car. The motorist himself can customize this combination.

To unlock the motor, depending on the immobilizer settings, you will need to press a couple of buttons on the steering wheel, center console, switch the toggle switch, press the button and pedal, etc. The block will then be released. The disadvantage of this method is that the hijacker can trace the driver's actions and repeat them.

Immobilizer comfort functions

Some immobilizers have additional convenient options. For example, a motion sensor will react that the car has started to move. If there is no tag nearby, the immobilizer will turn off the engine, as if the hijacker is not getting under way correctly. In such a modification, the thief may not even know that this is a protection. A car equipped with such sensors can be started remotely.

If you turn off the electrical system of the car (disconnect the battery), then the immobilizer will also block the operation of the motor. Additional protection is also provided by the trunk and hood locks connected to the immobilizer.

When the immobilizer is connected via the CAN bus, the device is able to control the central lock. When a mark approaches the car, the doors will automatically unlock (this function also needs to be configured).

How to bypass the immobilizer

Some motorists sometimes need to bypass the immobilizer. For example, due to the operation of this device, a failure of the auto ignition system occurred. Of course, bypassing the immobilizer is possible only to the detriment of maximum protection against theft. Here are four legal ways.

1 method

The easiest and most inexpensive way is to use an additional tag key. The car owner hides it somewhere near the immobilizer and fixes it securely so that it does not roll anywhere while driving.

In this case, the immobilizer is permanently disabled and the driver only uses the alarm. With such a protection bypass scheme, the motor will never be blocked from unauthorized starting, unless the car owner installs an additional lock.

2 method

A high level of security when bypassing the immobilizer can be achieved by installing an official bypass unit. In this case, a signal from the control key fob is sent to the autostart system, so you can start the engine remotely.

What is an immobilizer in a car and why is it needed

3 method

One of the most radical methods of bypassing an immobilizer is removing it from the system. This procedure cannot be performed on your own, because the electronics of the car can be seriously damaged. A car with a remote immobilizer also lacks maximum protection.

4 method

Another of the most acceptable methods is a special bypass block. This device has its own key fob. On a signal from it, the unit turns off the immobilizer and the car can be started.

Regardless of the method chosen, it must be borne in mind that tampering with the electronic immobilizer system can seriously damage the car. Therefore, the installation of additional equipment must be carried out by specialists.

Which is better: immobilizer or alarm?

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

IMMO4 (1)

Given these factors, it cannot be said that it is better because signaling and IMMO are not interchangeable. Do not think that the presence of an engine start lock is a reliable protection against theft. A thief may try to steal a car in other ways, for example, by hacking and towing it to another place.

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

What is the difference between a regular immobilizer and an expensive one?

In case of an unauthorized attempt to start the engine, a standard immobilizer can block the fuel system, ignition, steering wheel or ECU. But when using a standard device, there is a high probability that an experienced hijacker will easily bypass the protection.

In more expensive non-standard immobilizers, non-standard schemes for shutting down various parts of the car are used, which greatly complicates the task of selecting a suitable bypass method. To disable the standard immobilizer, some people use devices that are used by emergency services.

Do I need to set an alarm if there is an immobilizer

The short answer to this question is yes - an alarm is needed, even if the car is protected by an immobilizer. The reason lies in the principle of operation of these protections.

As for the operation of the immobilizer, it blocks the operation of the motor if there is no transponder in the range of the receiver. Depending on the model of the device, it can also block the transmission or various electronics (fuel pump, ignition, etc.). But the operation of this device does not prevent people from entering the car interior.

The thief may not steal the vehicle, but he can either damage the panel by trying to steal the on-board computer or other equipment installed in the car.

What is an immobilizer in a car and why is it needed

If an alarm is additionally installed in the car, then the thief will have less time to steal something from the car or try to bypass the immobilizer. When using a signaling with a feedback key fob, the driver immediately knows that his car is in danger (depending on the distance of the car from the key fob). The immobilizer is unable to do this. He simply does not give the opportunity to leave by car.

Possible problems with the immobilizer and their solutions

If we conditionally divide all problems with immobilizers, we get two categories:

Software breakdowns are characterized by all kinds of software failures, the appearance of various errors in the operation of the microprocessor. Also, a software failure will occur if the signal is out of sync between the control unit and the transponder.

The category of hardware breakdowns includes all kinds of malfunctions associated with a breakdown of the control unit microcircuit or a break in the communication bus (it connects the control unit, actuators and wiring of the auto systems to be blocked).

Before trying to find out on your own the cause of the failure of the immobilizer, you need to diagnose the electronics of the car. The very first thing you need to pay attention to is the battery charge level. If it is low, then there is a high probability of incorrect operation of the immobilizer.

Further, it is necessary to take into account that the device will work correctly only with the original transponder key. If the car owner tried to create some kind of copy of the key, then he can either transmit the wrong signal, or it will come with failures.

You also need to make sure that the failure of the immo is not associated with the connection of additional electronics in the engine compartment. Additional electronics can interfere with the operation of the control unit. If such equipment has been installed, then it can be temporarily turned off and the blocking can be checked for operability. When you restore the functionality, the reason is obvious: you need to either turn off the additional equipment, or install it in a place where it will not interfere.

What is an immobilizer in a car and why is it needed
IMMO error.

The reasons for the incorrect work of the immo or its refusal are:

  1. Dead battery;
  2. The battery was disconnected when the ignition was turned on;
  3. Violation of synchronization in the operation of the engine and immobilizer control units. This often happens after replacing the power unit;
  4. Immobilizer fuse blown;
  5. Errors in software. If an immo error lights up on the panel, but the car still starts up stably, then you still need to seek help from specialists so that they can find the cause. Otherwise, the device will stop working due to a large number of errors, and the control unit will have to be reprogrammed;
  6. Battery discharge in the key;
  7. Broken transponder;
  8. Loss of contact between the receiver and the antenna (usually due to shaking or oxidation of the contacts);
  9. Burst of wiring.

What to do if you have problems

Regardless of what kind of breakdown was formed in the immobilizer system, specialists in the service center should deal with its shutdown, repair and reprogramming. If the device is repaired by unskilled workers, this can only aggravate the situation.

In some cases, even a failure of the car electronics is possible if the immobilizer is turned off incorrectly. If reprogramming is necessary, the car owner must know the PIN code that is provided with the vehicle during the purchase in the salon.

If the car was bought on the secondary market, and the previous owner lost this code, then the new owner is advised to request a pin code from the automaker and reconfigure the immobilizer. This will give confidence that no one was able to "steal" the blocking signal from the previous car owner.

Of course, when ordering such information, the new car owner must submit all documents confirming that he is now the legal owner of the vehicle.

How can a stock immobilizer be “strengthened”?

Despite the fact that an immobilizer in a car provides reliable protection against vehicle theft, it has a significant drawback. The device does not block the desire to steal a car. Experienced car thieves find ways to bypass the immobilizer or how to make it work on a signal from a nonexistent ignition key.

For this, different devices are used that read codes or bypass the lock. To make an attempt to steal a car problematic, a motorist can take the following steps:

What is an immobilizer in a car and why is it needed

Of course, additional elements that block free access to the control elements of the immobilizer require investment and some installation work. But when an attacker is tempted to hijack a vehicle, the extra protection will catch him off guard.

Possible malfunctions

All immobilizer malfunctions can be conditionally divided into software and hardware. If the software fails, even when an attempt is made to start the power unit, the electronics can block its operation. This is due to a violation of the synchronization between the immobilizer control unit and the machine's ECU. Such malfunctions are eliminated by flashing the key fob and the immo control unit.

In the second case (hardware failure), any element of the system fails. This can be a burned-out microcircuit, a wire break, a broken contact, and similar breakdowns.

Regardless of the type of breakdown, it is not recommended to try to fix it yourself if you have no experience in carrying out such work. Only a professional can determine what the problem is with the immo, and then only with the presence of certain equipment. For this, the chip key and the immobilizer control unit are diagnosed.

How to bypass the immobilizer?

This procedure may be required in case of breakage or loss of the chip key or in case of technical malfunctions, but there is no time to go to the service station. To temporarily (and some bypass the immo on an ongoing basis, believing that their car does not need such protection) bypass the immobilizer, you can use one of the following methods:

  1. A crawler is installed that uses the original chip key.
  2. Install the crawler paired with a copy of the chip key. This method is used most often today.
  3. A special unit is installed that broadcasts a copy of the signal from the chip key.

If a crawler is used, then a chip from the original key must be installed in it. There are also keyless models. In them, the module is tuned to the signal from the key and then transmits the signal to the immo unit via an encrypted channel.

How to replace the immobilizer

If the elements of the immobilizer 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 is out of order. However, you need to know exactly where each component of the device is.

What is an immobilizer in a car and why is it needed

It is worth considering that many immobilizers have several modules that are 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.

Safety Precautions

As we have already paid attention several times, any work on installation / dismantling requires special skills and knowledge in auto electronics. Therefore, installation or repairs must be carried out in specialized service stations.

Since an unscrupulous workshop worker can copy a chip key or a signal from it, it is better that this is either a person you can trust, or the workshop should be far from the place of operation of the vehicle. This will prevent the hijacker from using a copy of the key.

When using the immobilizer, you need to make sure that there are no dubious persons nearby who are sitting at a laptop near the car (if a chip key is used without a master key). There are readers on the black market that can be used by a hijacker.

Advantages and disadvantages of the immobilizer

IMMO5 (1)

Anti-theft system is important for the safety of the car. The harder it is, the higher its reliability. What are the benefits of installing IMMO?

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

Despite the high reliability, this device has a significant drawback. If a key card or a keychain with a chip is used, it is enough for a thief to steal them - and a new owner has appeared in the car. In case of losing the key, you can use the 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 take advantage of access to the machine for his own purposes.

The following video reveals 10 common myths about immobilizers:

Questions and answers:

What does an immobilizer look like? The immobilizer has a microprocessor block with wires running from it. Depending on the model of the device, it additionally has a sensor to which the key card is held. In modern models, the control element for locking the car systems is built into the key body.

How does the immobilizer work? The main task of the immobilizer is to prevent the power unit from starting or stopping in the absence of a key in the signal field of the control unit. This device should receive the signal from the key card. Otherwise, the blocking is not deactivated. You cannot just cut the wires and the immobilizer is disabled. It all depends on the connection method and on which systems the device is synchronized with.

How do I disable the immobilizer? The process of disabling the immobilizer without a key is expensive, and in a car service that provides this service, you will definitely need to provide proof that you are the owner of the car. The easiest way is to register an additional key. But in this case, if the original key was stolen, it is better not to do this, but to configure the device for a new kit ordered from the automaker. You can deactivate the device by entering a code combination (it can only be given by the manufacturer of the device), a special device or an emulator.

9 comments

  • Angeline

    I am genuinely delighted to read this blog posts
    which carries plenty of helpful information, thanks for providing such information.

  • grant

    Today, I went to the beach front with my children.
    I found a sea shell and gave it to my 4 year old daughter and said “You can hear the ocean if you put this to your ear.” She placed the shell to her
    ear and screamed. There was a hermit crab inside and it pinched her ear.
    She never wants to go back! LoL I know this is totally off topic but I had to tell someone!

  • Bryan

    Thanks for your marvelous posting! I really enjoyed
    reading it, you can be a great author.I will be
    sure to bookmark your blog and will often come back in the future.
    I want to encourage one to continue your great work, have
    a nice day!

  • Luca

    When I originally commented I clicked the “Notify me when new comments are added” checkbox and now
    each time a comment is added I get four emails with the same comment.
    Is there any way you can remove people from That service?
    Thanks a lot!

  • buy n95 masks

    You come up with some insightful points within this article, but are you lacking something contextual?

  • anonym

    do I need advice… if I replace the lock on the switch box do I need to replace the reading coil from the old lock as well? well thank you

  • Zachary Velkov

    hello, since I have a problem with the immobilizer, I recently had a new key programmed in a volkswagen, my question is if I keep the key in the car all the time, will it be a problem

  • John

    My car does not start just after changing the battery, it is discharged, it is a Toyota vitz 2 from Kinshasa DRC

Add a comment