1999 E46 318i car do not want to start. Computer box motherboard is burned where the no 1 plug fits. Can i replace the computer box with a second hand one and is it a question of plug and start or what is the procedure.

Turn key not working but all dash lights work

You can fit a new one from scrapyard but you will need the chip from the key and the transponder to make it work ,a new one in dealers is around a 1000euros and a dealer will not reprogramme a secondhand one for you as they only want to fit a new one (profit) Unless you can find a local auto locksmith who can reprogramme the immobilisor for you but for him to do this you will need the chassis number of the donor vehicle so he can get the 4 figure code to reprogramme the key to the ECU immobilisor .