Whirlpool dwf 406

HiI have a problem with my whirlpool dwf 406. It starts, fills up with water, sloshes about a few minutes, drains, beeps and stops. It does not open the dishwasher tray.When it sloshes about it sounds like the arms are hitting something, but when I check them they are swinging freely.I’ve tried pressing the start-button for 10 seconds. No change.This happens no matter what program I select.The only buttons that are lit up are the salt and the softener indicator, plus the selected program and the start button. The start button does not flash.I’ve tried putting in some salt, it doesn’t help.The vitals are:8542 406 01710and 33 0135 002307Help please!