Kenmore Ultra Wash dishwasher 665.17779990 left a lot of water in bottom yesterday. When I pressed drain button, I heard pump come on for 2 seconds, then stop. After 1 minute, pump again came on for 2 seconds and stop. Did this once more, then drain light went off. What do I check first?

When I first got it it was working fine. Now it won't drain, leaving dirty water on the bottom. I don't think the pipe is drained because I push the cancel/drain button and it then drains. What should do?