How do I determine if it is the pump or the motor?

First you need to turn electricity to dishwasher off. Then you need to check the drain hose where it connects to drain line. Sometimes they are clogged there. If it is not clogged there, then you need to take the bottom cover off of the front. Take the drain hose off of the pump. Be prepared to catch some water in a shallow drain pan. The plastic piece the drain hose was connected to could have something stuck in it. This piece can be removed by unscrewing it counter clockwise. If there is nothing in it then you probably have a bad pump. The pump and motor comes as one piece. I hope this helps you.