This is one I haven't heard before. I had been getting a "Trailer wiring fault" message on my F350 and narrowed the problem down to the right rear wheel. After taking off the hub I found that, sure enough, the magnet wires had been severed. After taking a close look, it seems that the cam on the actuator arm is missing! I don't see how it could have come off and there were no bits or pieces in the hub so it seems like it was never there.
Anyone seen this before?
Pic 1 - trailer brakes
Pic 2 - missing cam
Pic 3 - right front brake showing where cam should be
