It is a thermal error, but typically only occurs when going through high temperature changes, as in leave it in the car for a few hours in a Canadian winter then bring it inside and turn it on sort of thing. It may happen in hot climates where the sun beats down and raises the temps, then the Air conditioner is turned on blowing on or near the printer.
It is possible I suppose that you may have gotten some dust in the vents on the printer, or placed a computer/laptop exhaust port near the printer sensor.
Are all components grounded properly? (Move to another plug and see if it clears)
Check and reseat all wiring to the Printhead. Did this correct the problem?
but these are just guesses of course. But might be enough to help you get it running.
My Phaser 8560 that has worked fine for years just started showing this error. I powered it off for a day or so and it came up ok and printed fine, but a day or two later and I have the problem recurring. What I get from the service manual is that the printhead thermal sensor indicates overheating. Makes no sense since the printer is not even warmed up yet. Any ideas on resolution, perhaps there is an error code that needs to be cleared? Do I need to take the unit apart and vacuum it out? Calling a Xerox specialist in will cost more than a replacement colour printer so I am disinclined to do this despite really liking the printer reliability up until now.
Any guidance will be appreciated.