Error code
HP LaserJet 79 Service Error: causes and fixes
An HP LaserJet 79 Service Error is a critical fault, often from a corrupt job, a memory module or firmware. Clear the jobs, check the memory, then update.
Printer display · HP
What it means
A 79 service error means the formatter, the printer’s main processing board, found a critical error and stopped until it’s restarted. Common triggers are a corrupt or incompatible print job, a memory module (DIMM) that’s faulty, loose or not supported by the model, an add-on card, or firmware that needs updating. Nothing mechanical has jammed: the fault is in the printer’s electronics or in the data they received. The digits after 79 vary by model and help narrow the cause.
When you’ll see it
- Soon after installing extra memory or an accessory
- On power-up, when a stuck job is resent
- When one particular file is printed
- After a firmware update or a driver change
- Now and then, with the same code each time
Usually caused by
- Most commonA corrupt or incompatible print job
- SometimesA faulty, loose or unsupported memory module (DIMM)
- SometimesFirmware that needs updating
- Less commonAn add-on network or accessory card
- Less commonA failing formatter board
How to clear it
Work down the list in order. Tick off each step as you go: your progress is saved on this device.
On the printer itself
0 of 7 tried
-
Note the code and restart
Write down the full message, including any digits after 79, then turn the printer off, wait 30 seconds and turn it on.
You should see: If it reaches Ready and stays there, keep printing but watch for a repeat.
-
Restart with all data cables out
If it comes back, turn the printer off, unplug the network and USB cables, and turn it on again. Staying Ready with nothing connected points to a corrupt job, so clear the queues on your computers before you reconnect.
-
Power off and open the memory access panel
If the error happens with nothing connected, turn the printer off and unplug it. Check your manual for the panel that gives access to the formatter and memory slots, and open it only if the manual treats it as user-accessible.
-
Reseat each memory module
Touch bare metal to discharge static, then release each module’s clips, lift it out and press it back in firmly until the clips lock.
-
Test with only the original memory
If you added memory, especially a module not listed for your model, remove it and test with only the factory-fitted memory.
You should see: No 79 with the extra module out means that module is faulty or unsupported.
-
Remove other add-on cards
Take out any accessory or network card added after purchase, close the panel, plug the printer in and test again.
-
Update the firmware
Once the printer stays Ready, download the firmware for your exact model from HP’s official support site and install it as instructed. Keep the printer switched on until it finishes and restarts.
Windows 11 and 10
0 of 5 tried
-
Open the print queue
Go to Settings > Bluetooth & devices > Printers & scanners, choose the printer and select Open print queue. On Windows 10, start from Settings > Devices.
-
Cancel all documents
Cancel every job listed. If one stays stuck on Deleting, move on to the next step.
-
Restart the spooler to clear stuck jobs
Open Command Prompt as administrator and run the command below, which stops and restarts the Print Spooler and usually drops a job that won’t cancel.
net stop spooler && net start spoolerYou should see: The queue window shows no documents.
-
Find the job that triggers it
Print a short Notepad page first. If that works, send your documents one at a time to find the one that brings back the 79.
-
Reprint the problem file another way
Save the problem document as a PDF with Microsoft Print to PDF and print the PDF, or install a different driver for your model from HP’s official support site and print it again.
Common questions
What is the difference between a 49 and a 79 error?
Both are formatter errors that need a restart, and both are often set off by a bad job. A 79 points more often to hardware such as memory or an accessory card, while a 49 points more often to firmware and data.
Can I use any memory module that fits?
No. LaserJets accept only certain module types and sizes, and an unsupported module can cause 79 errors. Check your manual for the supported memory.
Why does the error stop when I unplug the network cable?
Because the trigger is a job or data arriving over the network. Clear the queues on every computer, then reconnect and watch which job brings the error back.