All colors print fine except black, it's very faint.
Calibration does nothing.
Toner full, black print drum replaced.
I do notice something new, black toner is piling up on top of the black print drum after running a 20 page job.
Go to Solution.
That would make it a developer housing issue, which isn't customer replaceable, you would likely need to call service, or buy the part through a 3rd party and google a copy of the service manual.