I have replaced both fans (main and EP fan),Replaced the system board and did a factory reset and still the error comes up every so often. Any solutions? Also how do you enter the serial number back into the printer after it looses it?

Are you an Lexmark authorized repair technician? Only they have a utility that is a bit encoded secured and copy protected.

You will have to call Lexmark Service.

This code is on a very restrictive list because product security and warranty
Claims fraud.