Hi
Thanks for reaching out to the HP Support Forums!
I understand that you're getting pink horizontal lines on color printouts. I will certainly do my best to help you and please remember to return to this thread and mark 'Accept as Solution', if I have successfully helped you resolve the issue. If you wish to say 'thanks' for my effort to help, click the 'thumbs up' to give me a Kudos.
I see that you have completed some troubleshooting already. You mentioned that "the diagnostic test comes back clear". It sounds like the ink cartridges are low (the ink level indicator is an approximate amount of ink in the cartridges).
- Clear as in, no horizontal lines or the report is blank?
If you signed up with the HP Instant Ink program, please do not replace the ink cartridge without using the Instant Ink cartridges. Please call our Cloud Services at 855-785-2777. If you live outside the US/Canada Region, please click the link below to get the support number for your region. http://www8.hp.com/us/en/contact-hp/ww-phone-assist.html
Please respond to this post with the result of your troubleshooting. I look forward to hearing from you. Good Luck! 