As people have said its an I motion, do a learn run on it but make sure your belt tension does not allow it to slip when reaches fully open or closed during the learn run or this will give you an encoder mismatch fault. Usually encored mismatch faults are given when somebody blocks the doors during nudge closing. I have twenty of these in a hotel that the housekeepers love to.block the doors with their carts. To clear press the up arrow once and the display changes to clear and restart or somesuch, press enter and your good to go.