HP Error 79
What the code means · Diagnosis at a glance
HP Error 79 (shown as 79 Service Error, Turn off then on) is an internal firmware error: the printer formatter hit an unexpected exception while processing data and stopped. It is most often caused by a corrupt print job, the wrong print driver, or outdated or badly installed firmware. On most models the printer tries to restart on its own, and a power cycle plus clearing the print queue resolves it. When it keeps returning or loops on restart, re-flashing the firmware is the reliable fix.
Affected brands & models
Diagnosis at a glance
Likely causes ranked, with severity and the recommended action.
What the code means
Error 79 is an internal firmware error. The formatter (the small onboard computer that turns your document into instructions for the print engine) hit an exception it could not handle and halted. On most current models the printer restarts itself and displays 79 Service Error, Turn off then on.
Because this is a data-processing fault rather than a broken mechanical part, it is usually cleared by removing whatever the printer choked on (a stuck or corrupt job) and by making sure the firmware and driver are current and healthy. Only a persistent 79 that survives a clean re-flash points to the formatter hardware.
Most frequent causes
- A corrupt or malformed print job reached the printer and crashed its firmware.
- A generic, mismatched, or outdated print driver is sending data the printer cannot parse.
- The firmware is out of date, or a recent firmware update installed incompletely.
- A surge protector, power strip, or weak outlet is not delivering stable power.
- A network print server, embedded service, or software add-on repeatedly pushes bad data.
Quick fix: try this first
- Turn the printer off with the power button, wait at least 30 seconds, then turn it back on and let it finish initializing.
- Cancel any stuck job on the printer and delete all documents from your computer print queue before printing again.
- Plug the printer directly into a wall outlet instead of a surge protector or power strip, then retry.
Step-by-step solution
0 / 7 doneTick each step as you go. Your progress is kept while you work.
Before you start
- Note your exact model number (on the label on the printer) so you download the right driver and firmware.
- Have a USB cable ready in case you need to re-flash the firmware directly.
What not to do
- ×Do not unplug the printer in the middle of a firmware update. That can corrupt it and cause a boot loop.
- ×Do not keep resending the same document that triggered 79; it may be the corrupt job.
- ×Do not open the printer electronics to fix a firmware fault: 79 is a software and data-processing issue.
When to stop & call support
Stop and contact HP support if the printer stays in a 79 boot loop after a power cycle, a factory reset, and a USB firmware re-flash, or if 79 appears the moment you power on with nothing connected. That pattern points to a formatter or hardware fault that needs service rather than a stuck job.
If the error comes back
If 79 keeps returning, look for the trigger. If it only happens with one document, that job or its source app is corrupt. Recreate it or print it as a PDF from another program. If it returns after every firmware auto-update, downgrade and turn off automatic updates so the bad build does not reinstall. Recurring 79 with no obvious trigger, after a clean firmware re-flash and reset, usually means the formatter board needs a technician.
Related parts & consumables
Questions about HP 79
Does 79 Service Error, Turn off then on mean my printer is broken?
Usually not. It is an internal firmware error: the printer choked on data while processing. A power cycle and clearing the print queue clear it in most cases; a stubborn one needs a firmware re-flash rather than repair.
Why did error 79 start right after a firmware update?
A firmware update can install incompletely or ship with a bug, leaving the printer in a 79 boot loop. Re-flash the firmware over USB, and if a downgrade fixes it, disable automatic updates so the bad build does not reinstall.
Will fixing error 79 delete my printer settings?
A power cycle and clearing the queue will not. A factory reset will erase Wi-Fi and custom settings, so only use it if the printer is stuck in a loop, and be ready to set it up again afterwards.
The error came back when I printed one specific file. Why?
That document is almost certainly the corrupt job crashing the firmware. Delete it from the queue, then recreate it or print it as a PDF from a different application.
Last updated · Content is independent and not sponsored by any manufacturer.
Sources & methodology
- HP LaserJet Pro: 79 Errors (official support) Manufacturer
- HP: 79 Error (or 79 Service Error), Turn off then on Manufacturer
- HP Support Community: 79 Service Error, Turn off then on Corroborating user reports
- The Windows Club: Fix Service Error 79 on HP Printer Corroborating technical write-up
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