Dell 1250c print issue

The image is of a solid black rectangle.  Until recently, this would be a solid black image.  Last week, I had a Color Toner Density Sensor error (which, by the way, was not listed in the user manual) which was solved by cleaning the CTDS (which WAS in the user manual).  Since that time, the printer will not print a solid black, even small black errors on photos.  Black printing of letters and numbers is satisfactory unless the font size used is huge.

I have used the cleaning brush on all four of the toner cartridge locations.  I have replaced the black toner cartridge with a new one.  None of these steps worked.  Dell support is nonfunctional as the printer's warranty apparently expired in 2013.  I am guessing that, given what I've read on the printer forum with other toner-using printers, that the CTDS error may be associated with a waste toner issue.  I do not know how the Dell 1250c handles waste toner.  Dell's solution is to replace the printer.  If I am forced to do this, it won't be a Dell printer that replaces it.  

I am asking the community for answers.  How is waste toner handled in the 1250c?  Is the buildup of waste toner responsible for the image above, and, if so, why is the coverage so ***?  How can this issue be fixed?  My goal is to be able to print photos again, but I cannot with the current status.

As a side issue, there is a squeak, squeak, squeak noise when the printer gears up to print a page until the page is printed and the printer goes into wait mode.  It's like a roller needs lubrication, but I have no idea which roller, what kind of lubrication, or how to determine where the squeak is occurring.  Any ideas?  I don't think the squeaking is fatal, but it is *** irritating.