Reinstall the imaging unit.
Remove the toner cartridge, and then the imaging unit.
Warning—Potential Damage: Do not expose the imaging unit to direct light for more than 10 minutes. Extended exposure to light may cause print quality problems.
Install the imaging unit, and then the cartridge.
Resend the print job.
Is the printer printing solid black pages?
Go to step 2.
The problem is solved.
Replace the imaging unit, and then resend the print job.
Contact customer support.