The 04 error code indicates that your dishwasher fails to dry your dishes properly. This happens when the relay, which is located on the control board, is not functional. In most devices, the control board is located inside the door and can be removed easily. Once the control board is removed, the relay is clearly visible. If you have a little experience with similar devices, you can do it yourself. However, if you are not sure you can complete such a task, address a qualified technician. This type of repair is not quite so expensive.