Kenwood kdw243a Dishwasher?

Can someone please tell me what error code E4 means on my kenwood kdw243a diswasher? The dishwasher is 2 years old. The drain pump is not swiching off at the end of the cycle unless you actually push the on/off swtich. Turning the dishwasher back on again, the drain pump cuts in and the Error code E4 appears in the display