Currently have an older DocuPrint CP305d which has been a great printer. It has started printing part of the page in faded black, not the whole page. It only seems to be the black as far as I can tell.
To date, at great expense, I have replaced the toner, the fuser, the drum and the feed roller unit all with new genuine parts and it has made no difference. I've been through the maintenance menu and reset/reregistered/re-everythinged I could find. I've cleaned the color toner density sensor and the feed roller inside the printer.
Nothing has made a difference. Is the printer just past its use-by date? I could have probably bought a new printer for the cost of the above new spare parts sadly.