Why did this happen?

[Boar-Ral]

Where are the actual sensors located? Are they located inside the axle casing, or at the actual wheel assembly? I have had my ABS light come on twice when offroading, and of course, because traction control relies on these sensors, everything shuts down. So I guess the root of the problem is something flaking out with the sensors, whether it be for the reasons others have stated, like excessive wheel spin, or something else. I was just wondering where the sensors were, because I was wondering if it was possible to get gunk in between them that might cause a problem. I am experiencing problems with the ABS sensors on my car at the moment, due to a wire harness that is almost torn out. Until the replacement gets here, it tends to flake out a lot right around freezing, when I think snow and ice melt and moisture gets in there. When it is really warm, or really cold, it is never a problem.