a step-by-step guide would be great.
i'm despairing on my dnx-4280bt
i found a way to update my kenwood dnx 4280bt map.
first you need a USB STICK MICRO CARD READER. plug to the radio and go to nav ,system , update , then radio gonna send a file to the usb stick.
go to kenwood website to update. select model.plug the usb stick.scan,then you see your radio model picture.
to have the map update for version 2015.20 gonna cost you £50.
is not the cheeper way but at least is legal map.