I am ECU programmer and I read the ECU's via OBDII but some ecu in order to be read they need boot mode... So, I found in your site elements for the ME7.3.1 - ME7.3.H4 ECU.
in some sites I 've found that the boot mode is Pin 20 of Tool A, and in your last post the "F20 - Preparation for Flash Programming" is the boot mode, but the picture that has been posted by Manson166 gives the boot mode from Pin 10 "F10 - Cruise Control ON/OFF". So I think is wrong!
also this picture is from Byteshooter flash programmer and it is wrong. Why? Download Byteshooter - V2.72.zip
it has all the pinouts from all the ECU's! In ME7.3 gives pin 20 boot mode.
change language "einstellungen/sprache/english
pick alfa romeo 156 ME7.3.1
go to "?" on tool bar and pick "pin outs"