1. bougth a spare GTV receiver
2. extracted the memory from the receiver
3. calculated the code to unlock the receiver
4. hooked up the receiver to an external power source
5. unlocked the receiver with the recently extracted unlock code
6. programmed the original GTV key to the receiver
7. disconnected the receiver
8. extracted the memory again and calculated the code for my real GTV key that I previously added to the receiver
Went to my beloved GTV, unlocked the receiver on site using a pen, then added two used one button blue Fiat Brava/Punto/etc remotes bought on Ebay to the receiver and voilá, now I have got three working remote keys that operates the remote locking system flawlessly
The blue Fiat one button remotes can regularly be found on Ebay, and the circuit boards come equipped with either PIC or ATMEL processors, both work with the remote locking receiver (I tested them on the spare receiver).
And as always, a working remote flashes constantly when pressing the button. I have a non-working remote and it flashes only once.