Kitchen Large Electric Appliances - Dishwasher/GE Potscrubber 720

Hi,

My Dishwasher stopped cleaning the dishes suddenly. This particular model has the tower in the center which raises up when in use, which leads me to believe the lower arm is probably not clogged. None of the holes in the lower arm appear to be blocked and I can't figure out how to remove it since raising and turning it either counter clockwise or clockwise is un-screwing it.

I was curious if there is an internal water pump that is possibly bad, or possibly an easy to fix problem. Also, if their is an internal water pump, is their a way to see if it is the problem before I bother someone to make a service call.

Thank you very much for any help!

between the spray arm and the tub are 2 square holes... stick in a screw driver and turn counter-clockwise.. probably clogged in the pump area... without the model number cant look up to see what all you got in there