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So it sounds like you know the error means that the washer doesn't think it's draining properly. It's possible that the drain pump needs to be replaced if you cleaned the trap, but you'll want to determine if the washer is actually draining all the water out or not. There is about half a gallon left in the tub and hose when it drains out properly and that is normal. But if you still have gallons of water left inside, then you'll want to replace the drain pump.
On the other hand, if you determine that it really is draining out and it's just giving you an error which isn't accurate, there is a pressure switch mounted above the washer tub to the right side panel of the washer that senses the water level and it's not sensing properly. Remove the screws coming in from the top panel of the washer and pull the top panel straight back, up, and off. Look for the plastic device attached to the right side wall that has a small rubber hose and several wires going to it---this is your pressure switch. Disconnect the hose and blow through it to make sure it's clear. Then try the washer again and if the error comes up, replace the pressure switch.
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alright good luck!