Most appliance makers publish a code and leave you to find out what it stands for. This one publishes a cause and a set of steps for nearly every code it has — which makes these appliances unusually approachable, and creates a specific trap: one published cause often covers a whole circuit. A drain code covers a filter, a pump, a loose cover, a kinked hose and an air gap, and four of those five are not a repair at all.
So the code gets you to the right page quickly. What it does not do is finish the diagnosis, and that is the part these pages are for.