It's not the bleeding process you're trying to accomplish. Example, if you lose brakes to the fronts, the combination valve will direct more pressure to the rears or visa versa. If the valve gets stuck on one side, it will activate the light. You're attempting to center the combination valve and bleeding may accomplish that. If it doesn't you may have to remove the lines (at the combo valve) and see if you can push something in there to center the combo valve.