I have replaced more Ford ABS modules/pumps for low pedal problems than I have for them failing electrically. I haven't ran into any newer models yet, but the older ones have black plugs on the side of the unit. Once you pop the plugs off you will need to put something in the hole (I use a piece of 3" long wire) until it bottoms out. Have someone start the engine and press the brake pedal. If the wire moves, the unit is bad.
These are the pistons that move and allow pressure to drop when ABS is needed, but should stay still under normal braking.
