HP LaserJet 79 Service error: firmware or print job error

Turn the printer off, wait at least 30 seconds and turn it on again. If it reaches Ready, cancel the job you were printing when the error appeared. If the error returned the moment that job resent, the job itself is the likely cause.

Cancel all waiting jobs on every computer that uses the printer. Then turn the printer off, disconnect its network or USB cable and turn it on. If it stays at Ready with nothing connected, reconnect it and print jobs one at a time to find the file or computer that triggers the error.

Make sure every computer uses a driver intended for your exact model, downloaded from HP's official support site, or HP's universal print driver if your model supports it. A driver for a different model can send commands the printer can't process. If the error started after a driver change, remove the driver completely and reinstall the correct one.

If one document triggers the error, save it as a new PDF, print it from another app, or print a smaller range of pages to find the page that fails. Very large images, unusual fonts and damaged files are common culprits.

Print a configuration page from the printer's menu to see its firmware version, then check your model's page on HP's official support site for an update and follow the instructions there. Don't switch the printer off while an update is installing.

If the error began after a memory module or other accessory was installed, turn the printer off and unplug it, then remove the part following the steps in your manual. Handle modules by their edges. If the printer works without the part, it may be incompatible or need reseating; check the part numbers your manual lists as supported.

If the error appears with no cables connected, current firmware and no added accessories, the formatter board or another part may need repair. Use HP's official support website for warranty and repair options, or your service agreement if the printer is under contract.