If the drain pump is running all the time then whats proberly happened here is water has leaked into the base and has activated the antiflood switch which keeps the pump running all the time.
What you need to do is either pull the dishwasher out and tip it backwards. This will allow the water to drain out from the bottom. So you may need a towel for this part.
Once the water is out the antiflood swicth will reset itself and the dishwasher should start to work ok from there.
Or as its built in you need to remove the wooden kickboard along the kitchen and then remove the metal/plastic cover at the bottom below the door.
From there you can use a sponge and soak the water up from the base. Now this part is a bit tricky as there isnt much room in there.
Once clear retry the dishwasher and see how it goes. If it does it again then theres a leak in there which you need to find and fix to cure the fault.
Check it out and see what you find. If you need anymore info just get back to me.