GE Dishwasher won't drain when connected to air gap

[drundell]

I cannot get my dishwasher to drain properly. I unhooked and cleared all visible debris from the inside tube and drain line. If I leave the drain pipe unhooked and at low elevation, the water drains out when put past the rinse cycle. There is only weak pressure (doesn’t seem to be pumping). Is this the solenoid or the pump? How can I tell?