I have no experience with this on Hondas... but, this sounds like a similar problem I had with my Pathfinder. It was the drain hose, and it was easy to fix. I just stuck a wire up through the drain hose and kind of moved it around. When I pulled the wire out, water starting draining out like crazy. It's just like snakin a pipe, but be careful not to rip the hose. I don't know if this helps or not, but it's just my $ .02.