Immobilizer and Coded Key: how they work and their failures.

In the past stealing a car was just a matter of breaking a lock, peeling and joining some colored wires and as a magic pass the engine went into operation.

In Brazil around the year 2000 cars were already being manufactured with an accessory that drastically decreased the number of vehicle thefts without the use of the key: The Automotive Immobilizer, also known as immo or anti-start.

The immobilizer currently consists of:

1: Key encoded with mechanical secret and transponder (in the transponder is saved the secret code that makes the car pick up, this is the famous “Chip”).

2: Immobilizer antenna, which can be coupled or not to a board with central command circuit. In some cases the plate is in a box hidden under the panel far away from the antenna.

3: Immobilizer command center: Controls the reception of the key secret code, and the recording of new keys, in addition to also sending a signal to the car computer (ECU – ECM) to allow the start.

4: There is also on the dashboard of cars a light shaped like a key, padlock or with the words CODE, or LOCK that allows quick diagnostics of the immobilizer system. It lights up by turning the contact key, and after the match should erase.  If the it is blinking repeatedly, or intermittently when attempting to start, and the car engine does not start up, it is very likely that there is a failure in the key transponder, or any other part of the immobilizer system.

The operating sequence is as follows:

When opening the car and inserting the key into the ignition contact the antenna is quickly electrified by a pulse sent by the immobilizer control center, which causes the transponder (chip) of the key to be fed, thus sending the secret code to the immobilizer’s antenna, the code is interpreted, and if it is correct, then a signal is sent to ECU , which in turn releases the pulse of the nozzles injectors, and electrical supply of the electronic injection system, allowing the engine to start.

If the code that is stored in the key is not the correct code expected by the system, after three attempts the system is temporarily locked and does not allow the start anymore.

More like not everything is flowers…

Like every anti-theft system, over the years it’s become lagging behind, and the loacupies and gatunos on duty are learning to master and bypass the system to steal the cars. Then all form of protection becomes valid to complement the immobilizer and prevent the car from being stolen.

Even with immobilizer system cars nowadays are stolen frequently, where the bandit simply rips off the ecu of the car, and inserts a modified ECU that does not need coded key to start and takes the car away in a few minutes.

You can complement the safety of your car with:

*A good automotive alarm that is well installed, try to acquire an alarm from a well-known brand, and look for an installer that is known to do a good installation, and you will surely make your car more difficult to steal.

*Install a vehicular tracker.  Because at worst if the car is still stolen you can still track it with the help of the police and recover it without major headaches.

*Take out insurance! For many insurance may not be the cheapest or most affordable option, more after living in Brazil, I think one of the best ways out is to hire this service.

Besides all that…

Electronic systems are successionable to failures over time, especially when we talk about cars, not least because they are directly exposed to the action of time, heat, solar radiation, rains, infiltrations, floods, and natural wear and tear.  That’s where the problem lives..

A faulty immobilizer system can cause a huge headache, not least because the parts are expensive, and there are few professionals with the knowledge needed to uncover defects in this new technology, considered too complicated by older automotive professionals.

Main defects:

Transponder failure: which can be intermittent, and sometimes caused by sudden drops of the car key on the floor, or in other cases caused by electromagnetic interference caused for example by the craze or simply lack of knowledge of the car user, to put the key on the refrigerator or other household appliance every day when arriving home.

Failure in the Antenna of the immobilizer of the car: That can be caused by the action of the heat of the sun of the large centers of the cities, which over time tend to make the conductive properties of the antenna different, changing the electrical resistance, and leaving a hairy intermittent defect, which makes the car hour work, time does not work.

Failure of electronic circuits, wiring of the car, or interference caused by poorly installed or poor quality accessories: Alarms, sound, or xenon kits poorly installed can cause difficult failures to be detected in the immobilizer, making the operation of the car unpredictable and flawed.

It is worth remembering that battery failures, and water infiltrations also damage the system.

In vehicles where it is no longer possible to pair new keys, or the immobilizer system no longer works as it should be possible to disable the immobilizer and make the car work without the need for a programmed key!  This procedure is called DECODE.

See an article on how to disable the automotive immobilizer here.

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