Most of today’s vehicles are equipped from the factory with a theft security system, which usually starting blocks motor. Several types:

  • Transponder Key
  • Infrared Remote Command
  • Keypad


The market demands increasingly safe cars, both from the point view active and passive safety, but also concerned about the security of property deposited inside and difficulty opposed to be stolen.

For these reasons and legal basis in some countries, automakers incorporate these systems to ensure that only the authorized user can make use of the vehicle. One of the most used systems is the immobilizer transponder type, due to its high degree of inviolability and that requires from the user, other manipulation in performance than the simple fact operate the ignition key.

What is a transponder immobilizer?

Immobilizer transponder is a system that only allows booting vehicle with authorized keys. Try it with any other key means that the engine starts, but it only works for a few seconds (in most cases). The reason is that its operation is based on blocking the engine control unit, if not the circumstances giving adequate, not excite the relay of the fuel pump and not active or the injectors or power stage ignition (Some Ford are an exception to the latter). Logically, the engine starting is impossible.

How immobilizer transponders work?

There are several versions that differ in immobilizer some components, but the principles of operation basically are very similar. In the transponder immobilizer system, the key incorporates a small chip inserted into the handle of the same and that issues a code for radio frequency at the time the contact is actuated. This code is captured by an antenna or DVD drive, usually located in the ignition switch. The captured by the reader unit code is sent to the control unit immobilizer, which proceeds to compare it with the one stored. Simultaneously, the engine control unit sends to turn the unit the code for you, and is also compared with the memorized.

The immobilizer control unit allows the boot drive engine control when the codes issued by the key and drive motor control coincide with those stored in its memory during the recording process. In the event that one of the two codes does not match, the control unit loses engine start authorization and the engine stops approximately two seconds after startup has started. These Ones two seconds in which the engine starts are needed because authorization code flow through a single cable between units control and engine immobilizer.

Obviously, these systems allow the adaptation of several keys and replacement of any faulty component using the procedures corresponding. In some cases the use of equipment will be necessary Special and other simply employing a master key. As already established, the immobilizer not required for any intervention operation by the user of the car without is that of activating the ignition key in the usual way, so much so that in many cases the customer does not relate the fact that the engine does not start with the presence of this system. The mechanic must be clear: if the engine starts well, works well for two seconds and stops quickly, is very probable that the cause lies in an immobilizer problem.


To be continued…


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