Lexmark C910 981 Service Switch Error

I fixed 2 printers with this error msg. the first printer had a bad sensor board which had to be replaced. Second time around required a lot more TLC because I had to replaced the belt up/down clutch. 1 word for that repair... screws.....LOTS AND LOTS OF SCREWS! You've been warned.

three things can cause this error...
the error normally comes about when the machine hasnt sensed the ITU has been engaged properly, therefore error appears, later releases of firmware(few years ago now) altered the timeing of the mechanism to allow if a longer activation period and this did work some of the kinks out.
first thou the firmware, if you are getting the error all the time though it can be tricky to update on the fly... but can still be done.
next cause is usally because somebody tampers with the little white agitator at the front of machine. The is directly connected to the belt up down clutch, if moved by hand, the clutch will need to be replaced. big job, but not hard.
next is the itu. if the waste toner is full or the lifting mechansism on the ITU has become clagged with debris and toner which constricts movement of clutch, then the error can appear...