KitchenAid KDTE254ESS1 Dishwasher Not Moving Spray Arms

[Steve762]

This dishwasher was working fine until about 1 week ago. First we noticed the soap dispenser having detergent left in it. Just a bit at first but got to the point where almost none of the soap was coming out in a wash cycle, and nothing was getting clean.  Water still fills and empties normally (and I've tried manually adding more water and it made no difference). Circulation pump runs but only a dribble comes out of the spray arms and they don't move (although they spin freely by hand).

I did the usual checks, removed a clog or two from spray arm nozzles, blew air thru the pipes up to the middle and top arms, took out the circulation pump and cleaned out some minor debris and made sure the impeller could turn. Seems to me the problem is most likely either the circulation pump (motor getting weak and/or impeller getting loose on the shaft) or the diverter valve not rotating and directing water to the various arms. I just don't know how to diagnose which it is; it's not like you can put a pressure gauge on the arm water and see how much you're getting.

So I am posting here, hoping for some ideas on how to narrow the problem down (or find other possible causes). Suggestions?

[Vance R]

Use the tech sheet that is stored in the toe plate area to pull error codes.  Did the inverter have corroded connection?