Whirlpool Dhw b10w?

Hi, About 15-20 seconds into a program on our Whirlpool DWH B10 W dishwasher, the machine bleeps and sounds as if it is draining. On opening the door we find that start button is flashing (indicating a fault occuring) and sometimes it also show a light on the pre-rinse. The drainage pipe and water fill have been checked and seem OK.The dishwasher is only used once a week and is just over a year old! any idea? Thank Paul