If you google Bosch E22 you will get many hits! Here's one I found:

E22 is residual water in sump, this could be blocked pump, dirty filter, grease build up. If you have removed white pump cover to check for blockages, ensure that it is completely clipped back into position before trying again. The non return valve maybe allowing dirty water to drain back into the machine. If you tend to run a quick wash a lot, you may need to boil a kettle and pour it into the sump to clear any build up from around the optical sensor in the sump.

Thanks Geoffrey. Clearly my most basic google skills failed me yesterday. I cleaned the filter and ran the cycle again with no problems.