Connections to the air-assist fan include the four spring-loaded contacts on the bottom of the print head module, which make contact with the four corresponding contact pads on the carriage plate printed circuit board. If one of those connections is not making solid contact, you can receive this error due to improper feedback. make sure that these contacts are clean and free of any built up residue. Wipe both the pads and pins with a Zeiss wipe, and scrub lightly with a pencil eraser, then reassemble and test.