HP Officejet Pro 251dw Printer series - Manual (Page 65)

If defects are seen on the Print Quality Diagnostic report, follow the steps below:
1.
If the Print Quality Diagnostic report shows faded, partial, streaked, or
missing color bars or patterns, check for depleted ink cartridges, and
replace the ink cartridge that corresponds to the defective color bar or color
pattern. If there is no depleted ink cartridge, remove and reinstall all ink
cartridges to make sure they are properly installed. Do not remove the
depleted cartridge until you have a new ink cartridge available to replace.
For information about how to install new cartridges, see Replace the ink
cartridges.
2. Calibrate the linefeed. For more information, see Calibrate the linefeed.
3. Align the printhead. For more information, see Align the printhead.
4. Clean the printhead. For more information, see Clean the printhead.
5. If none of the previous steps have helped, contact HP support to replace the
printhead. For more information, see HP support.
Cause: Print quality problems can have many causes: software settings, a poor
image file, or the printing system itself. If you are unhappy with the quality of your
prints, a Print Quality Diagnostic page can help you determine if the printing
system is working correctly.
Solution 7: Contact HP support
Solution: Contact HP support for service.
Print quality troubleshooting 61