I have a 98 540 (manual) and have been having a problem with the traction control light.
Here's the deal, a few months ago the car started jerking while driving and then the traction control light would come on. The jerking wasn't to one side, just felt as though the brakes were slammed and then the light came on.(I don't know if the brake lights came on or not) So I tried replacing one of the wheel speed sensors in the front and it seemed a little better but now it is doing it again. (Sadly I live in Michigan and the car doesn't do so well in the several feet of snow we received so I didn't really get an opportunity to test it out too much.) Last night it did something else too...
Last night after starting it the traction control light was on. I started driving and the car was very sluggish and was jerking forward. It took a lot of gas to smooth out the jerking. It stopped after I went around the block, but this is the second time it has pulled the sluggish/jerking move (the first time I thought I was just imagining things)