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Russell H.
Russell H., Printer and Office
Category: Printers
Satisfied Customers: 12226
Experience:  11+ yrs experience, inkjets & lasers, from huge to portable
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On MP540 printer error message UO52 appears. Apparently this

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On MP540 printer error message UO52 appears. Apparently this means that the print head is incorrect, but this has never been touched ever
Thank you for asking your question here at My name is XXXXX XXXXX I will do my best to answer your question today.

The first thing to try for this problem is, to open the printer,
remove the cartridges (all of them) and set them aside on their sides,
then remove the printhead (by lifting the lock lever, then lifting the printhead out)
then put the printhead back in and push down the lock lever,
then put the cartridges back in, close everything up, and try the printer again. Cycle power Off for about 5 minutes first, though.

If that doesn't change the problem, then take cartridges and printhead out again, and this time clean the copper-colored or silver-colored contacts on the printhead, using fresh cotton swabs moistened in rubbing alcohol, never touching the contacts nor the inky underside of the printhead with your fingers, and never touching the inky underside of the printhead with anything.
Then reassemble the printhead+cartridges, close up, turn Off for 5 minutes + , then turn On again, try again.

If that doesn't work, then you might need another printhead... or more than that. A new printhead might cost quite a lot... so if it comes to your wanting to try that, let me find out for you how much this printer's printhead costs.

Also if the printer is still less than a year old, then it is covered by Canon's warranty and will be repaired for free by them, if you put in a failure-within-warranty claim on the printer before the year (since purchase) is out.
Russell H. and 2 other Printers Specialists are ready to help you
Customer: replied 4 years ago.

Tried what you suggested but to no avail.Why would print head suddenly pack up?

There could be various factors - but, if you changed cartridges while wearing wool clothing, or while standing on a glass sheet, or with the printer set upon a glass sheet, or perhaps a vinyl sheet in either case, or on a very dry not-humid day or indoor conditions, static charge may have transfered from your fingers through the cartridges to the printhead, damaging its (rather minimal) internal circuitry.

Or if your printer was powered by directly plugging it into the wall, a power surge may have damaged circuitry, probably in the interface to the printhead, even if that is less likely.

If I can advise you further on this matter, let me know.

If the case is finished as far as your need for advice from me is concerned, I would appreciate it if you could rate my Answer - hopefully favorably - so that I may be paid for the work I have done on the case.