Something like this ? DSC warning (or DSC disabled) ?
DSC unit failure @ 60k miles... - Page 5 - BMW 3-Series (E90 E92) Forum - E90Post.com
Or is is the speed limit warning light (you can set the max speed of the car via the idrive menu)

DSC unit failure @ 60k miles... - Page 5 - BMW 3-Series (E90 E92) Forum - E90Post.com
Or is is the speed limit warning light (you can set the max speed of the car via the idrive menu)