Inside every key there is a small chip called a “transponder”. In most cases this chip does not require an external power supply, it is supplied by a magnetic field, which induces an electric current. The immobilizer recognizes whether a proper key is used to start a car exactly by using the transponder. With the evolution of the VAG cars the transponder type and the records inside it have changed. In general, there are five different types of immobilizers/transponders used.

They are called Immo I, Immo II, Immo III, Immo IV and Immo V. Systems from ImmoI up to Immo III require that a transponder from the appropriate type is located inside the key, and they are able to learn these transponders.

Starting from Immo III it is required that the transponder is from the proper type, but also has some specific records inside it. Only transponders with such correct records can be learned.

According to the data inside there are the following types of transponders

• Tp22 – dedicated for use in Seat vehicles;

• Tp23 – dedicated for use in Volkswagen vehicles;

• Tp24 – dedicated for use in Skoda vehicles;

• Tp25 – dedicated for use in Audi vehicles (especially A3 and A4);

Such transponders can be used in all cars of the specific manufacturer (e.g. Tp24 can be used for all Skoda models);

The lastest immobilizer systems Immo IV and Immo V require that the transponder is programmed with a specific code, and this code depends on the VIN number and is unique for each car. Normally, only the car manufacturer can deliver such keys and they are called “dealer keys” (because only the dealer can supply them). But the ABRITES Diagnostics for VAG is also able to pre-code the transponders/keys so they becomes the same as the ones purchased from the dealer.