Check the drain hose and make sure it is not plugged or kinked
Check the drain pump filter for debris
Check the drain pump
If all the above checks out good . This would indicate that the pressure switch or also called the analog pressure sensor has failed. First you will need to remove the top lid. Usually 2 or 3 screws on the back and the top comes right off. The pressure switch has a clear hose and a clump of wires going to it located on the right hand side. Then unplug the hose and blow thru it it should be clear. Check the hose for leaks or obstructions. Also in the back of the washer on the left hand side is a air dome this is where it gets it pressure reading from, make sure it is not obstructed.Make sure the connection is good. Make sure there is no visible damage to the air dome. If all is clear the pressure switch will need to be replaced. Here is a link to help with accessing the pressure switch #20 in the diagram, also if you need diagrams or illustrations of your particular model enter your model # above.