HP LaserJet Pro M375/M475 — 79 Error Turn off then on
The printer encountered an internal firmware error and stopped the current operation.
Error meaning
The product experienced an internal firmware error.
This meaning is tied to the reviewed family/platform and subsystem below; do not reuse the number or wording by itself on a different printer family or protocol.
Applies to
LaserJet Pro 300/400 color MFP M375/M475 Series
- HP LaserJet Pro 300 color MFP M375
- HP LaserJet Pro 400 color MFP M475
Common formatting
These are formatting/lookup aliases for this reviewed condition, not separate error pages.
- 79 Error Turn off then on
- 79
What usually causes it
- A particular print job, file, font, or data stream triggered a firmware fault.
- Network or accessory data reached the printer in a state the firmware could not process.
- The printer firmware itself is outdated or in a bad runtime state.
What to try
Turn the printer off and back on
Use a normal power restart first. Do not repeatedly power-cycle if the same job immediately recreates the error.
Retest without resending the original job
If the printer reaches Ready, print a simple internal or test page before reopening the document that triggered the failure.
Isolate the triggering job or source
If only one file/application causes 79 Error, recreate the document, try a simpler driver path, or clear that queued job rather than replacing hardware.
Check HP firmware if the error repeats broadly
Use HP's current supported firmware path for the M375/M475 family. Keep accessories and network changes in scope only if the timing points to them.
After each corrective action
Retry the same operation that produced 79 Error Turn off then on. If it now works, stop there rather than changing unrelated printer, network, supply, or service settings.
If the code returns
If 79 returns with no queued job and after a normal restart, disconnect optional data paths one at a time where safe and document whether the fault occurs at idle or only when processing work.
When service may be needed
A persistent 79 firmware error after job isolation and current firmware may need HP support. Avoid formatter-board or internal electronics repair guidance for a general user.
Continue with guided troubleshooting
If the printer still is not working after the reviewed checks, carry this verified error context into the guided troubleshooter.
Related information
Verified source
Official HP family support document explicitly covers M375/M475 and provides supply and 79-series control-panel meanings/actions. Color variants are reviewed as variants, not separate SEO opportunities.