oh you mean "DS" mode, not DSC (that's dynamic stability control). It's most likely a broken wire inside shifter assembly. it takes about an hour or so and a piece of spare wire to fix yourself.
search for DS mode and you should find a few threads about it.
EDIT:
here, I'll save you some time
http://www.e90post.com/forums/showth...=447680&page=2
here is a pic of mine when I fixed it a few months ago.
