I had BMW F10 with MSV90 , I made a full backup of the original DME (Pflash and Dflash) data and wrote it on the donor one ... The car start perfectly with no issues . SO why did you open the DME for writing ISN ??? I think the process should be same with msv80 ... I think your way is used when the original DME is no longer communicating and no data and ISN could be taken from ...