What does Canon Pixma MG8220 error 6C10 mean?

It is my pleasure to guide you.

I have done some extensive research on your 'error 6C10'.

I have looked at the following:

QUOTE

PIXMA MP500 Printer
Canon Pixma MP500 Service Manual
http://www.printermanualguide.com/canon-printer/canon-pixma-mp500-service-manual.html

2-2. Service Call Errors (by Cyclic Blinking in Orange (Alarm LED) and Green (ON/OFF button), or Alarm LED Lit in Orange)

Cycles of blinking in orange (Alarm LED) and green (ON/OFF button) 16 times

Error [Error code] Valve sensor error [6C00]

Conditions An error occurred in the valve sensor during cleaning.

Solution(Replacement of listed parts, which are likely to be faulty) - Logic board ***'y (QM2-3078)
UNQUOTE

I realize that the '6C00' error is not exactly your but the manual does not have the 6C10. You can download that at the above link.

I also look at the http://www.retrevo.com/support/Canon-MP500-Multifunction-Printers-manual/id/259bh640/t/2/ Canon Pixma MP500 Users Guide Manual. There are several codes but not the 6C10. You can download this above as well.
Good luck and please post back that you are successful, giving thumbs up, or if I can be more helpful.