Frigidaire dishwasher won't drain completely

[WarpedHardwood]

Relatively new (< 1 year) Frigidaire model FGID2466QW4A, always has 1 - 1-1/2 inches of water in bottom when wash is finished. Doesn't appear to be related to selected cycle - all do it. There's plenty of water draining according to observation at disconnected drain coupling at main sink drain - lots of water pumping out! But always some left in basin, dishes are also not appearing to be well cleaned - this may be subjective. Any suggestions / help greatly appreciated.

[16345Ed]

Sounds like sump needs taken apart and checked for debris. Also possible failed check valve allowing water back in from drain. 

[WarpedHardwood]

Thanks for the response. Would either or both of these be reached from within the basin, or under the machine? Is a service manual available?

[WarpedHardwood]

Problem solved... disassembled everything internal, found nothing. Disconnected drain hose at pump outlet and found three pistachio shells...... thanks for the support.