Can anyone help here?

I've got a GE Dishwasher that thinks it's clogged. The BLOCKED DRAIN
light comes on even though the motor/pump works perfectly and drained
the water out of the tub. After a few minutes the pump stays on and the
BLOCKED light comes on. I've also checked the float/overflow and drain
solenoid switches and they are ok.

What else would cause this?

Thanks,

Steve

The Model Number is GSD3000w16.