If most of your pages are coming out with a fog or haze of toner on them it generally means that you have a defective toner cartridge, but that is not always the case. In certain situations it could mean there is a damaged printhead cable. If replacing the toner doesn’t get you the print quality you seek, try replacing this instead.
One way you can confirm this issue without inspecting the cables is to
switch the Print Resolution setting from 300 or 600 dpi to 1200 dpi, and vice versa. If
switching between 300/600 dpi and 1200 dpi improves the appearance of the printed
pages, replacing the laser cable assembly will likely correct the issue.
NOTE: This can be a useful diagnostic tool in cases where you are walking a customer
through diagnosing this issue or otherwise cannot visually inspect the printhead cables.