I have a freightliner with a abs light on when I go to hook up scan tool comes on for a second then shuts off. I hear the wabco controller clicking when tring to come on, also the abs light goes off when headlights are on?? could the controller be bad???
The headlights are probably DRLs, and one of the ways they can be activated is when someone releases the parking brakes. Perhaps there is a crossed/shorted wire?