Hey, so I did the job myself and fixed all problems. I was unable to do a DIY, but I did learn and confirm quite a bit.
As a refresher, I drive an 2009 e92 M3, and a few months back, I had three warning lights come on the iDrive screen:
1. Braking/Chassis stablization malfunction!
2. DBC malfunction! Drive carefully
3. Start-off assistance inactive!
Additionally, the cruise control would not work and I was getting the yellow ABS, Brake and triangle with the arrow encircling it, and the ((ABS)) warning.
The car drove normally. I didn't notice any noise. I took it to Dinan, and after a relatively expensive diagnosis, they told me that I a left wheel bearing assembly was defective.
I first tried replacing the sensors, and cleaning out where the attach to the hub. It was a cheap and easy job--but it was not the problem.
So I ordered bearings from a site called partsgeek.com. They were about $90 per wheel, and new axle nuts (about $9). I also went to Harbor Freight Tools and purchased a bearing separator (about $20) and Front Wheel Bearing Adapter kit (about $100). And after a lot of trial and error (and maybe a little cussing), I replaced both bearings.
I got into the car, and took it for a test drive. Everything was great with the ride, but all of the same lights came on--and more. The word "Brake" turned red, and the Airbag light came on, and I had no speedometer.
I ended up purchasing a second set of bearings from BMW (about $140 each), and interestingly they looked identical to the Timkens I purchased previously. Turns out that the first set I purchased were boxed incorrectly (or??) because they did not have the magnetic sensors. I put in the BMW bearings, and drove the car--and everything is back to normal. All lights out, and speedo and cruise control work again.
So this is what my experience suggests.
1. If you get the three lights, you need to replace a rear wheel bearing.
2. If, in addition to the three lights, your speedo doesn't work--its your right rear wheel bearing that is bad.
3. If, in addition to the three lights, your cruise control doesn't work--is your left wheel bearing that is bad.
4. If, in addition to the three lights, you have no speedo, no cruise control and your Airbag lights come on, then both rear bearings need to be replaced.
5. Although special tools are needed to do this job, it is possible to do as a DIY. The special tools you will need cost $120, and are pretty readily available. It can be pretty physical, but it is not all that complicated.
6. Although replacing the sensors is easy, they are probably not the problem. And no, cleaning them out will not fix the problem.
7. The system will reset itself when it gets a consistent signal from both wheel sensors.
When I get a chance, I'll see if I can do a walk-through from memory.