Sounds like either your float is either hung up,the float switch is bad,or your water valve is leaking.
Click on the link for tutorials on all three....how to check and replace.
Click on the link
Appliancehelponline.com
On the heading at the top of the page click on "repair videos"
Click on the blue highlighted words reading Checking the Float and Water Inlet Valve
This is a generic video but applies to all dishwashers in principal.
If you forward your complete model number I will be able to show you where these parts are located on your machine.