For the entire season I didn't have ABS and my ABS lights were flashing, I tried everything suggested even by BMW mechanic but nothing worked. I was convinced I had a bad module so I just rode the entire season this year with the lights flashing and the ABS not working. Just tonight I sat down and I was actually looking for a video on YouTube on flushing my rear brake fluid when this video come up in the suggestions: 'Clearing a fault from BMW ABS I & ABS II systems' (the brake Gods must have been watching me!). I watched it and decided to give it a try just now and it worked! I now don't have the flashing lights and ABS IS working.

Many people have problems with flashing ABS light and ABS not working, this is one thing that is a must try.

Video here: (Credits to Chris Harris BWM guru)