I would expect the 6100 to be the same as the 5000 in this issue. With the iPF5000 it seems that cleaning the printhead DOES NOT help with the error message. On the canonwiki site there has been a few posts with check nozzle warnings and running printhead cleanings did not help. The only thing that helped was replacing the printhead.
The only variable is, I believe, that the iPF6100 has the PF-03 printheads where the iPF5000 had the PF-01 printheads. I would still suspect that running printhead cleanings will not help.
I have this error on my iPF5000, I have not ran a printhead cleaning do to the posts on the canonwiki that mention that cleanings do not help.
Here is an old link from the wiki talking about the subjecthttp://canonipf.wikispaces.com/message/view/FAQ/783401
I had early failure printheads on my 5000 just before warranty expired, and they were replaced with the new Teflon coated PF-3's. Repeated cleanings did nothing but waste ink. No problems with the new ones past 18 months.
Be ready to be horrified at the ink used in old head purging and new head refilling - make sure all tanks for the affected head are preferably above 40% as about 20% per channel is used as I recall, and that the MT has a lot of capacity left.