I happen to own Bosch dishwasher and one day it started to act up on me. It started to fill/drain continuously. The problem was infamous “impeller jug” http://www.espares.co.uk/part/dishwashers/bosch/sgs53c02gb%2f15/p/1083/856/0/998660/754220/dishwasher-impeller-jug.html, device that measures amount of water that is let into machine. This device consists of impeller that has magnet attached to it and reed switch that is switched on and off by the magnet attached to the impeller. Reed switches sometimes get stuck and that is exactly what happened to mine. Temporary fix is to pull out board with reed switch from jug casing and give it a few taps, as well you can do a few passes over strong magnet. Semi-permanent fix is to replace reed switch (it will get stuck eventually again, thus semi-permanent) with one like this http://uk.farnell.com/jsp/search/productdetail.jsp?sku=1079468 and avoid spending 20 GBP or equivalent of your local currency on unnecessary plastic.