Cought a cold last week and got some time to dig into the Alfa Romeo M2.1 ECU fitted in some 166 and some 156 with V6 engine. 

I managed to turn of the immobilizer function in the flash. It's a simple change of two bytes to their compliment, however I don't know how the checksum is calculated, and where the checksum value is located, so I had to to it the dirty way by changing an unused area to get the same checksum as the original file.

Does anyone know how the checksum is calculated for this ECU so I can do this in a more proper way?


Attached is original and immo off BINs.