Mine happens under braking. It is intermittent, both light braking and hard braking. I tried to pull the speed sensors from the hubs, but the 10 mm bolts are corroded into place (broke one) and the speed sensor is like glued in place. Could not remove without destroying. Tried to clean magnetic pickups in place with electronic cleaner and compressed air. No difference to speak of. I may pull the fuse and drive as a non ABS vehicle, not sure yet. My quess is a speed sensor has some crud on it.