Replaced a lot of these on audi/vw's for this fault. repair kit comes from vw for about £130+vat and is half the body of the abs unit. very easy to replace but abs ecu and steering ansle sensor must be recalibrated which is a tad tricky (vag com can do this though) if the unit from atp is repaired for £180 and doesnt need recoding after that may be the easier route to go down,not a hard job to do though.
sean