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So this error means that the microwave thinks one of the door switches has failed. There are 3 door switches behind the front frame of the microwave where the hooks from the door itself go into. You'll need to test each switch with a multimeter by opening and closing the door to see if the switch is functioning properly. If not, then the faulty door switch needs to be replaced. If for some reason all the switches do check good, you'll need to order and replace the main control board because the display control board isn't reading the door switches properly.
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