HP Designjet 510 Printer series - Manual (Page 62)

Printhead errors
The front panel can display the following error messages for the printheads:
NOTE: An unknown error is displayed when one of the printheads is causing a problem but the system
cannot detect which one it is. Refer to
Unknown printhead error to solve this problem.
Printhead
missing
Faulty
printhead
Printhead
worn out
Unknown
error