My Whirlpool side by side fridge freezer wasn’t working found that PCB Board in the back had burnt marks on it, So bought a second hand one, plugged it in and it works ie compressor and all the fans kick in,and it cools the fridge and freezer, But after a few minutes I got a “CF” Error message flashing on the screen, looked online and apparently front control PCB needs to changed aswell for both to work together, so bought a brand new one, plugged it and I’m getting the same CF Error message, Also no water is dispensing and no ice, I’ve checked all the wiring to the front and back PCB Boards, the connector ontop of freezer door, everything seems connected as it should, the error goes away when I open the door or press the water dispenser, also pressing the temp buttons for fridge and freezer revert back to -18 freezer and 5c for the fridge. Please can someone help.

Ricky, August 2023

Don't know from where the suggestion came that both boards needed to be changed to work together. In your case you've got a secondhand back board and a brand new front one so you've still not got a "matching pair" even if you needed one.
Have another look at the Comms wiring. See
http://www.northlondonappliancerepairs.co.uk/error-codes/whirlpool-error-codes/error-codes-for-whirlpool-fridge-freezer.amp.html
That web page also points to their own dedicated forum for white goods, which might be a much better place to ask.

Rnfjfj, August 2023