Dell 2330D/DN, 2350D/DN Print is too dark, or the background is gray., White lines appear on the page.

You are using paper that does not meet the printer specifications.
The toner cartridge is low on toner.
The toner cartridge is defective.
Try the following:
Select a different Toner Darkness1 setting before sending the job to print.
Load paper from a new package.
Avoid textured paper with rough finishes.
Ensure that the paper you load in the trays is not damp.
Replace the toner cartridge.
Print is too dark, or the background is gray.
The Toner Darkness1 setting is too dark.
The toner cartridge is worn or defective.
Try the following:
Select a different Toner Darkness1 setting.
Replace the toner cartridge.
White lines appear on the page.