I found the solution myself. Underneath the machine, there is a plate. On the plate, there is a float and a microswitch, when the water leaks onto the bottom plate it raises the float and activates the microswith which shuts down the machine and shows E4 on display. To get rid of the fault, you have to pull out the dishwasher, then tilt it, and drain the water from the bottom plate. Also make sure that there is no leak in the internal piping, if there is, the fault will come back as soon as the recess in the bottom panel fills with water.Hope it helps.