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Replacement parts for General Electric GSD3400G00WW Dishwasher | AppliancePartsPros.com

I am assuming that the drain is properly installed and that the unit used to work OK.

Remove the kick plate so you can see the wash/drain solenoid (item 497 in Section 3)

The solenoid should be in the up (wash) position.
Start a cycle and watch it.
When it comes time for a drain, the solenoid should pull down.
When the unit has drained the springs should pull it back up to the wash position.
If it sticks in the down position then as it fills the unit will pump out the water.

The way it works is that at the start of the drain cycle the timer sends power to the solenoid for a few seconds. This pulls it down moving the flapper valve in the pump to the drain position. The water pressure then holds it there till the water is pumped out and then the sprigs pull it back to the wash position.

Could be that the solenoid is sticking down.

One thing to note is that sometimes the timer can power the solenoid for too long overheating it and melting the plastic in the solenoid causing problems. So if this is what is causing the sticking then both the solenoid and the timer should be replaced.