HP · Firmware / printer-side
HP LaserJet 79 / 79 Service Error
HP documents 79 errors as internal firmware-related errors on supported LaserJet models, with troubleshooting that includes power cycling and isolating the printer from network/USB input if the error persists.
Start hereIf the printer reaches Ready after you disconnect network/USB cables, the trigger may involve firmware, an incoming job, or the connected environment rather than a permanently failed print engine.
What to check
Step 1
Power the printer off, wait at least 30 seconds, and power it back on.
This is HP's first recommended action for 79 errors.
Step 2
If a surge protector is being used, follow HP's model-specific guidance.
HP's general 79 guidance may instruct plugging the printer directly into a wall outlet.
Step 3
If the error persists, turn the printer off and disconnect network/USB cables.
Power it back on while isolated. If it returns to Ready, do not immediately factory-reset it.
Step 4
Check the exact model's firmware/support page.
HP specifically recommends checking firmware when the printer starts normally while isolated.
Step 5
Reconnect methodically.
If the error returns only after reconnecting or submitting a particular job, record that trigger. Model-specific HP instructions should control the next step.
Verified sources
Printer Triage is an independent troubleshooting reference and is not affiliated with HP. Use the exact model's manufacturer documentation when instructions differ.