Prusa Error Codes: Reading the Number, Fixing MMU Jams

Every Prusa error screen on the MK4, MINI, XL, CORE One and MK3.5 carries a five-digit XXYZZ code that tells you the device and problem category, and for MMU2S and MMU3 owners the 04xxx family shows whether a stopped multicolor print needs a cleaned filament path, a checked cable

In this episode you'll learn:

• Newer Prusa firmware on the MK4, MINI, XL, CORE One and MK3.5 shows the error name, a short description, a five-digit code and a QR code that opens a dedicated Prusa Knowledge Base article for that exact error.
• The code follows the XXYZZ pattern; Prusa's own documentation uses 12201 as the example, a MINI bed heating failure shown on screen as 'Heating failed bed'.
• The first two digits identify the device, and 04 is reserved for the MMU unit (both the older MMU2S and the current MMU3); the third digit is the category: 1 mechanical, 3 electrical (typically motor drivers), 4 communication, 5 system states including incompatible firmware.
• 04402 is the general MMU communication error and 04504 is a firmware update request; mechanical errors in the 041xx range are the most common in practice, usually triggered when the FINDA sensor or the extruder filament sensor does not see filament where expected.
• The most common cause of MMU jams is a badly formed filament tip after it is pulled out of the hotend, and Prusa lists which printers show QR error codes in its public Prusa-Error-Codes repository on GitHub.

Read the full guides on our site: Prusa Error Codes Explained: MK4, MINI, XL and Core One · MMU Error Codes 04xxx: Why Multi-Material Jams and How to Fix It

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