2000 Montana ABS light

My abs and corresponding traction light goes on intermittently. I don't have to move the car or touch the brake for it to come on. Is there some common problem to point in a direction such as a bad sensor or electronic problem? Where is the sensor located?

In my 2000 Montana i was seeing the same thing. I was able to read the code and found it to be low brake fluid which upon further checking was rear brake cyliners leaking.
The Oil reservoir has a low fluid sensor that when the the car stops and starts the level changes in the tank.