You have to pull the knob real hard, don't afraid it won't break. Once the knob is removed you have to pop the trimming surrounding the module. It's held on by clips. If you do a search there's a prior post with information where to get a used idrive control for $75. I already tried cleaning and even took it apart. Save yourself the trouble and order a use one that's exactly what i did after attempting to fix it. Got it to work for like a few days but it'll start to fail.

http://www.xoutpost.com/bmw-sav-foru...d-press-2.html