Alfa/Fiat key system.
The original concept.
Transponders are supplied by makers ie Megamos, Philips, etc. and all are pre-programmed and locked, and all have a different
code in them. Master key and regular transponders are identical except from the codes in them.
The term key programming is confusing, as said the keys are pre-programmed and cant be altered, but these key codes must be
loaded into the cars immobiliser which is often called "programming the keys".
I will refer to entering the keys into car as "loading" rather than programming.
When the new car is originally loaded with keys, the transponder of the first key in becomes the master and all the remaining keys
are regular keys.
At this time no blank transponder keys were available, so any replacement key had another unique code in it, and the new key
needed the well known "master, red1, red2, master" sequence to load it into the car. As any replacement key is unique another
master key cannot be obtained, so ecu, immo, lockset etc are required just to add a key if the master is lost.
Then came the after market ...
Transponders became available which could be tailored (programmed) to simulate the protocol of a manufacturers key, thus
a clone could be made which operates exactly like the original. This meant that the master key was not required, because the
key that made the clone is already loaded into the immo.
Loosing all the keys was still a problem, however this can can be overcome in several ways.
1. Making a clone from the immobiliser information.
The immobiliser is opened and the data is extracted from eeprom, this data is used to make the clone key, (master or
Similarly data can be taken from a known good key and entered into the immo, (but not master key by this method).
2. The complete system ecu, immo and at least 1 working key can be taken from a breakers yard.
The above transponders use the static key system, where the same data is sent every time the key is operated, and is the most
simple around, however its very effective and has practically stopped vehicle theft because the thief has to get a key to get
The cloned keys work exactly as the original, though I find that if the transponder used in the Alfa is a Philips it seems to respond
better than the universal types.
Modern keys use a complicated calculating system, which changes data on every usage. The keys cannot be read, only written to
in most cases, so codes are required from manufacturer, and diagnostics are required to load the keys in.
Sorry its so long.