I finally dug into this problem last week and wanted to post my results. Somewhere (I thought here) I read that rust would push the sensor up just enough to cause a weak signal (voltage) to the computer. Most of the people that had this issue reported that the ABS was kicking in as they came to a stop, which was the opposite of what was happening to me. Regardless, some people with my issue said the fix worked for them too, so I gave it a try.
The goal was to remove the wheel, calipers, caliper bracket and rotor. Then remove the sensor. Clean the rust from the hub where the sensor mounts, hit with some paint and put it all back together. I didn't see a lot of rust when I removed my sensor but cleaned it up anyway. I also cleaned the sensor which had a little "crust" on it and bearing grease on the tip. I did this to both sides. The wheel bearing grease on the passenger side didn't look as good as the drivers side, but neither wheel had movement when I pulled at 12 and 6 before the work started.
It's been a little over a week and the problem as not returned. My thought on what happening: When there is rust buildup between the sensor and the "teeth" that pass near it, the voltage is low enough that it thinks the wheel has stopped (when it hasn't) and the ABS kicks in. In my case, I think there might be some metal contamination of the grease, which when built up on the end of the sensor will cause voltage to be too high. This will cause the computer to think the wheel is spinning and kick in the traction control.
So, what I'm saying is: if you have issues with ABS or traction control and suspect the wheel speed sensor, I recommend simply cleaning the sensor up before replacing it. My repair was free, although if it was metal bits in the grease it means I might have to do it again or my wheel bearing might not be long for this word.
