Because the door would no longer stay shut and didn't firmly click when closed. Reviewing reports on-line narrowed the problem, so I ordered the door lock assembly kit. Two Torx bits are needed: T10 for two screws that secure the gray latch/lock and sensor to the stainless interior wall of the door & T20 for twelve screws holding the control panel & decorative metal front to the interior wall. Pay close attention to theT20 screws, they aren't all one length. Remove the eight T20 screws holding the right & left edges of the metal front to the interior wall & slide it down and away from the interior wall. Carefully remove four T20 screws across the top edge that secure the control panel & allow it to gently swing forward & away from the interior wall. Remove the T10 screw on either side of the gray door lock part at the top edge of the interior wall. Remove the old gray door lock part from the interior panel, detach the two conductor cable connector, reattach the cable connector to the matching new part, and place it back in the interior panel and secure with the T10 screws. Then reattached the control panel & metal front to the interior panel in the reverse order of their removal. Next, remove two screws used to secure straps at the top of the dishwasher to the underside of the counter top & slide the body of the dishwasher out of the cabinetry until you can access the metal cover secured with four Philips-head screws. Remove the metal cover & lift the left side of the light colored door lock part up & slide to the left to remove it. Place the new matching part where the old was removed, replace the metal cover, & secure the four screws. Slide dishwasher back in place & reinstall screws securing it to counter top.