Dishwasher doesnt shut off, goes through 30 min cycle and doesnt turn off.

fast wash which is a 30 minute cycle goes down to zero and then it turns back on again and went to 15 mins cycle…. for the 15 mins cycle then goes through another wash cycle….so the 15 mins wash it went down to zero and everything drained and there is no water in it now so it works on the 15 min cycle and not the 30 mins cycle (wont turn off on 30 mins but shuts off on the 15 min cycle)….for the 30 mins has to shut off manually which then leaves water in the dishwasher