Abstract: A powered closure drive mechanism is provided for moving a closure between open and closed positions. An elongated housing extends between first and second ends that are movable in opposite directions toward and away from each other. A rotatable lead screw is disposed longitudinally within the elongated housing. A reversible motor rotates the lead screw in a first direction and a second direction to urge the first and second ends of the housing toward and away from each other. A sensor assembly includes a worm fixed to the lead screw for rotation therewith and a rotatable gear meshingly engaged with the worm. The worm and gear are geared such that the gear rotates less than one revolution in response to the closure moving between the open and closed positions.