GE profile partially drains

I have a ge profile GSD4134Z04WW that will not drain completely. The drain solenoid and plunger was sticking. Springs wouldnt quiet pull flapper or solenoid wouldnt move it all the way. Replaced solenoid I believe it works properly now. Drain cycle solenoid snaps flapper with 120 vac for about 8 seconds and flapper remains in drain until it sounds like water is out and springs pull it back. Open dishwasher ther is a small amount (1/2" or so) of water left in tub. I rinsed again watched solenoid when springs returned it I manually went back to drain and held it ther a while. Same thing water still in tub. Motor is running entire cycle. Whats wrong? Thanks

Here are your parts
Body parts replacement parts for GE GSD4134Z04WW | AppliancePartsPros.com

Could be the Piston&Nut Item 564 in Section 1 is leaking.
This is a common problem.
It is under the cover inside at the back of the tub. It unscrews.

These units never pump out totally dry as the pump seals will burn out if it rums while dry (there is always water in the sump).

[quote=denman;148909]Here are your parts
Body parts replacement parts for GE GSD4134Z04WW | AppliancePartsPros.com

Could be the Piston&Nut Item 564 in Section 1 is leaking.
This is a common problem.
It is under the cover inside at the back of the tub. It unscrews.

These units never pump out totally dry as the pump seals will burn out if it rums while dry (there is always water in the sump).[/quote]
What does the piston&nut do? Took it out looks to be some sort of check valve? pushed plunger up and the rubber valve is chewed up on edges and does not seal completely. I guess I will order that part. thanks

It circulates/drains some of the water back into the system/pump when in a wash cycle. During drain it must close so that all the water is directed to the drain hose.

Thanks I will let you know when I replace it.