So the problem is solved.
Strangely enough, the SA 249 MFL code was already missing from the factory in the FA, although 544 with an MFL was also available from the factory. Although I removed 544 about 3 years ago and inserted 5DF or ACC in the FA, the function was still there without an error message until recently. Nevertheless, it now works thanks to entry 249 with the coding of the individual control units FEM, Kombi, Icm.. Without error messages/problems.
P.S. (Sometimes the search for the cause of the error can be very short, but if you don't know it, the search, as with all activities, is very time-consuming
)
Thanks for your help.