Morse Code–Like Output and Random Character Printing Issue on HP Printer During Idle and Print Jobs

[kimkorton36]

Hello everyone, I’m facing a strange and persistent issue with my HP printer that I’m hoping someone here can help clarify. Recently, the printer has started producing unexpected printed output that resembles Morse code patterns—short and long lines, dots, or repeated characters rather than normal text. This happens intermittently and does not seem tied to any specific document type or application. The printer was working normally before, and no major hardware changes were made.

The issue appears both when sending standard print jobs and occasionally when the printer is idle but connected to the system. In some cases, a page prints with seemingly random dots and dashes arranged in sequences, almost like encoded signals, instead of the intended content. I initially suspected a font or driver problem, but the behavior persists even after switching fonts and printing simple test pages.

I have already tried basic troubleshooting steps such as restarting the printer, power cycling it, updating the printer driver, and testing with a different USB cable and port. I also reset the printer to factory defaults, but the Morse code–like output still occurs. Printing from another computer on the same network shows similar results, which makes me wonder if this could be related to firmware, memory corruption, or a communication protocol issue.

Another detail worth mentioning is that the problem becomes more noticeable after the printer has been powered on for a long period or after waking from sleep mode. This made me think of timing, buffer, or signal interpretation errors, where the printer may be misreading incoming data streams and translating them into repetitive symbols.

Has anyone encountered a similar issue where an HP printer outputs dot-and-dash patterns or repeated symbols resembling Morse code? Could this be a firmware bug, encoding mismatch, or a sign of failing hardware (such as the formatter board or RAM)? Any guidance on advanced diagnostics or specific settings to check would be greatly appreciated.

[Kuroi_Kenshi]

Hi @kimkorton36,

Welcome to the HP Support Community! We're stoked to have you on board! 

To help us get started on resolving your issue, could you please share the model name of your device?

We're looking forward to helping you get back up and running! 

Best regards,

[kimkorton36]

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@kimkorton36 wrote:

Hello everyone, I’m facing a strange and persistent issue with my HP printer that I’m hoping someone here can help clarify. Recently, the printer has started producing unexpected printed output that resembles Morse code patterns—short and long lines, dots, or repeated characters rather than normal text. This happens intermittently and does not seem tied to any specific document type or application. The printer was working normally before, and no major hardware changes were made.

The issue appears both when sending standard print jobs and occasionally when the printer is idle but connected to the system. In some cases, a page prints with seemingly random dots and dashes arranged in sequences, almost like encoded signals, instead of the intended content. I initially suspected a font or driver problem, but the behavior persists even after switching fonts and printing simple test pages.

I have already tried basic troubleshooting steps such as restarting the printer, power cycling it, updating the printer driver, and testing with a different USB cable and port. I also reset the printer to factory defaults, but the Morse code–like output still occurs. If you want to use morse code translator then click here. Printing from another computer on the same network shows similar results, which makes me wonder if this could be related to firmware, memory corruption, or a communication protocol issue.

Another detail worth mentioning is that the problem becomes more noticeable after the printer has been powered on for a long period or after waking from sleep mode. This made me think of timing, buffer, or signal interpretation errors, where the printer may be misreading incoming data streams and translating them into repetitive symbols.

Has anyone encountered a similar issue where an HP printer outputs dot-and-dash patterns or repeated symbols resembling Morse code? Could this be a firmware bug, encoding mismatch, or a sign of failing hardware (such as the formatter board or RAM)? Any guidance on advanced diagnostics or specific settings to check would be greatly appreciated.

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the printer model is HP LaserJet Pro MFP M428fdw. The issue occurs across different applications and even when printing internal test pages, which is why I’m leaning toward a firmware or formatter-related cause rather than something application-specific. I’ve already updated to the latest available firmware from HP’s site, but the behavior still appears intermittently, especially after sleep or long uptime.

[Kuroi_Kenshi]

Hi @kimkorton36,

Thank you for confirming the printer model and for the detailed explanation of the issue. Based on your observations, especially the behavior occurring on internal pages and after sleep or long uptime, please follow the troubleshooting steps below to further isolate the cause.

Perform a full cold reset with storage initialization
Power off the printer, then power it back on and immediately press and hold the Back (←) button until the printer displays a storage or initialization message.
This reset clears internal memory areas that are not erased during a standard factory reset.

Disable sleep and energy-saving features temporarily
From the printer control panel, set Sleep Delay to “Never” and disable energy-saving options.
Monitor the printer for 24–48 hours to check whether the issue is triggered by sleep or wake cycles.

Print internal diagnostic pages only
Print the Configuration Page, Demo Page, and Supplies Status Page directly from the printer menu.
If dot-and-dash or random symbol output appears on these pages, it confirms the issue is internal to the printer.

Isolate network and data input sources
Disconnect the network cable or disable Wi-Fi, then print internal pages again.
This helps confirm the issue is not caused by incoming network data or queued jobs.

Reinstall the firmware using the latest available package
Reapply the latest firmware for the HP LaserJet Pro MFP M428fdw using the HP firmware update utility.
Firmware reinstallation can correct incomplete or unstable firmware blocks.

Leave the printer powered on continuously for testing
Keep the printer powered on without allowing it to enter sleep mode for an extended period.
Note whether the issue only appears after long uptime or specific power-state changes.

Observe frequency and pattern of the output
Track when the dot-and-dash patterns occur (idle, after sleep, or during printing).
Consistent recurrence under the same conditions indicates formatter or memory instability.

If the issue continues after completing all steps above, the behavior is consistent with an internal formatter or memory-related condition rather than a driver or application issue.

I hope this helps.

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Best regards,