This is an ink system error.
First check the ink cartridges. Replace any that are low or empty. Remove the cartridges one at a time and check that the vent (on the top of the cartridge near the HP logo) is open. Remove any part of the orange tab that was left on by accident. If the vent is clogged, use a pin to unblock it. Then reinstall the cartridges and make sure that they snap into position. Close the access door and check the printer status in the control panel.
Attempt to run the printhead cleaning utility from the HP Solution Center (under Settings > Print Settings > Printer Toolbox).
Remove the printhead and clean it. Remove all of the cartridges, then lift the latch handle. Pull the printhead straight up. To clean the printhead you need lint-free clothes (coffee filters will work) and distilled or bottled water. Dampen the cloth with the water and wring out the excess. Then wipe the electrical contacts moving up towards the nozzles until all the old ink is removed. Do not touch the nozzles. Then clean the edge between the contacts and the nozzles, moving right to left (with the contacts towards you). Finally clean the ramps working away from the nozzles. Dry all the cleaned areas with another cloth.
Use another dampened cloth to clean the contacts inside the printer (move in a top to bottom motion). Then dry the area. Reinstall the printhead and lower the latch. Then reinsert the ink cartridges and close the access door. Check for the error again.
The next step to try is to reset the printer. With the printer on, unplug the power cord from the unit. Unplug the cord from the wall outlet as well. Wait at least 15 seconds and then reconnect the power cord to the wall outlet and then to the printer. Press the power button if needed to turn on the unit.
The final step to try is to replace the printhead. Unfortunately, if a new printhead doesn't work, the unit needs service and the printhead is not returnable.
There are pictures for the above solutions here: http://h10025.www1.hp.com/ewfrf/wc/document?docname=c01458034&lc=en&dlc=en&cc=us&product=3737195#N65
I hope this helps.