That's what im saying if the abs box has air trapped in the system it will leave no pedal height. I had to bypass mine in order to firm up my pedal because I couldn't get the air out of it. It was more of a question, how do you bleed it? Can you actuate it while not moving?
If the abs unit is actually working ok, you could pound the brakes a few times on a dirt road to get the abs to cycle, then bleed the brakes like normal.
Or drive over 3mph to let abs initialize then jack up all 4 (without turning engine off) and spin one or two tires and hit brakes to cycle each....then bleed.