Can you keep using it?
Can you keep using it?
Contact customer support if any of these apply
- !79:04 returns after a restart and direct connection check.
- !The printer still fails after a firmware update.
What to check first
Step-by-step checks
- 1
Safe first step
Unplug the power cable, wait a few seconds, and power the printer back on.
Start with the official recovery step before moving on to parts or deeper servicing.
- 2
Safe first step
Remove switchboxes and connect the printer directly to the computer if you can.
- 3
Safe first step
Update the printer firmware if 79:04 returns.
Background
What this message usually means
HP describes 79:04 as an unexpected generic firmware error. The official flow is to restart the printer, connect it directly rather than through switchboxes, and update firmware if the code comes back.
Before the message
What users usually notice first
Messages like this often appear after the printer fails one of its normal startup, supply, or paper-path checks and cannot return to ready state cleanly.
Diagnosis
Likely causes
An unexpected firmware-side fault occurred.
An indirect connection path or switchbox is interfering with the job flow.
The printer firmware needs to be updated.
Service
When service or replacement is more likely
- -This is one of HP's stronger signs that firmware or the job path, not paper loading, is the first place to look.
Avoid wrong turns
Common misreads of this message
- -Treating the message like a confirmed failed part instead of a support clue about which system has stopped the printer.
- -Assuming no physical path issue exists just because no full sheet is visible at first glance.
See also
Related codes in this family
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Read this next
Helpful guides for this problem
Guide
When a printer says paper jam but there isn't one
What a false paper-jam warning usually points to, from hidden scraps and tray issues to faults that are no longer simple jams.
Guide
How to tell if a printer fault is a cartridge issue or a service issue
How to separate ordinary cartridge or toner trouble from the kind of printer fault that usually points to real service.
Guide
How to find the right printer model family before using error codes
How to match the right printer family or series before trusting an error page that might only be a near match.
Boundary
When to stop troubleshooting and move to support
Use the message once to classify the problem, then move to support if the printer still cannot return to ready after the first safe checks.
Keep browsing
Where to go next
Source notes
HP's official DesignJet 100/110 article says 79:04 is an unexpected firmware error and recommends restart, direct connection, and firmware update.
Built from HP's official DesignJet 100/110 error-code article and the related support guidance for the 100, 100plus, 110 Color, and 110plus variants.
Printer error codes can vary a little by firmware, region, and exact model variant. Use this guide as a family-level starting point and stop if the next step would require disassembly or service-mode changes.
Known family variants: DesignJet 100, DesignJet 100plus, DesignJet 110 Color, DesignJet 110plus
Last reviewed: 2026-04-12
Reference: Open reference