Hi My GE Triton III GDS5260 dishwasher will not drain, this is what I have done so far:
1) Hoses are clear
2) Piston check valve assy thingy new
3) drain pump new

Took hose off exhaust outlet and ran a rinse/cancel, no pressure coming out of
outlet (just gravity drain) except just as washer finished cycle a brief shot of pressure.

Does this then indicate a sequence switch?

Your description sounds as though you've correctly identified the switching circuit as your machine's cause for not performing the final drain sequence.

Some dishwashers have a front panel button allowing manually triggering a drain cycle. If you do that when the wash sequence ends but before heating coil drying, you might be willing to live with that manual intervention step as a solution.

But I've seen heating coils operate over water-filled dishwasher sumps due to final drain failures like what you've described. The result is often lots of steam and water vapor production with poorly-dryed dishes. One with a black front and front air vent developed an unsightly white surface covering around that air vent. Anytime I see one of those, I immediately expect to find a drain system problem. After correcting the drain problem, cleaning the black plastic front with vinegar or another acid cleaner like Lime-a-way restores the clean black appearance.

More information for you. The choice of how to deal with it is yours.
John