I have a AEG L75480WD washer dryer fault pnc: 91460660500 th?

I have a AEG L75480WD washer dryer fault pnc: 91460660500 that is faulty. The unit over 10 years old. The fault code showing is E66. If the code is attempted to be reset this trips the RCD in the consumer unit.
The heater elements been checked and have resistance of 66ohms across the terminals when all wires are disconnected. Also checked the resistance between the elements and earth on the machine and both heater elements read open circuit so there is NO short circuit of the heater elements. A brand new control board on the right of the machine been replaced but the error remains the same E66. Thus, the fault must be generated elsewhere in the machine. I think the electrical suppressor may be faulty. What do you think? Are you able to suggest what to check next?