I have a DWF415 Ikea dishwasher from Whirlpool. It has started giving an f4 error where the start led blinks 4 cycles. The machine seems to go through a full cycle although does not seem to dry as well as it used to and gritty residue is left on the contents and the inside of the door.
Service manual says f4 means clean the filter but filters are all clean.
I checked, water is being pumped out of the machine at a good rate, the waste pipe does not look restricted at all. I ran the machine again yesterday and everything works fine, fills, heats water, the cycle lasts the correct time 120mins but it seems to be at the end when the f4 appears, maybe the drying cycle? the contents are never totally dry.