Final update. I replaced the water inlet valve and it seems to have done the trick. I'm not getting an error in the diagnostic cycle anymore and the dishes seem to be coming out cleaner. I guess that the valve was working, but not working to the level that it needed to be. It's difficult to tell based on sound along, but it definitly sounded like there was more water swishing around in there now. So, the dishwasher might be noiser but the dishes are cleaner.