HP Deskjet 6122 Color Inkjet Printer - Manual (Page 98)

automatically cleaning print cartridges
If your printed pages are missing lines or dots, or if streaks appear, the print
cartridges need to be cleaned.
Print cartridges are cleaned automatically using the following procedure:
1. Open the hp inkjet utility .
2. Select the Clean panel.
3. Click the Clean button, then follow the onscreen instructions.
If your printouts are still missing lines or dots after cleaning, a print cartridge may be
low on ink. One or both print cartridges may need to be replaced.