What's wrong with my dishwasher?

I have a Kenwood KID60B10 dishwasher. The last two days it's been turning itself on and off after the cycle has finished. Yesterday it showed an E9 error, and the control board flashed and beeped for about 30 minutes until we managed to switch it off.
Tonight, it did the cycle, then started all this up again 55 minutes after I'd finished using the machine. Can someone please tell me what E9 error is, and how do I go about fixing it? Thanks