HP DesignJet 100/110 error 79:04

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.

If the printer still starts normally: Finish the first checks once, then stop if the same message repeats or the printer still cannot return to ready.

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.

Diagnosis

Likely causes

Most common

An unexpected firmware-side fault occurred.

Common

An indirect connection path or switchbox is interfering with the job flow.

Possible

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.

Related codes in this family

01:10

The electronics module reported a failure.

95:00

Printhead alignment failed and the process was cancelled.

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Where to go next

Back to DesignJet 100/110 series

Browse the rest of this printer range and compare nearby messages.

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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

79:04 - An unexpected generic firmware error occurred.