Prusa error 13601 (Unknown Error) appears on the MK4 and its equivalents are #31601 on the CORE One, #35601 on the CORE One L, #26601 on the MK4S, #27601 on the MK3.9S, #21601 on the MK3.9, #28601 on the MK3.5S, #23601 on the MK3.5, #17601 on the XL, and #12601 on the MINI. The firmware encountered an error condition that does not match any defined error code in the current firmware version.

What the Error Means

Prusa’s firmware maps a large set of error conditions to specific codes with dedicated descriptions and recovery instructions. When the firmware detects a fault that falls outside these mapped conditions — perhaps due to an unexpected state in a newly released feature, an edge case triggered by a specific print file, or a code defect — it raises a generic Unknown Error rather than silently failing. This is a catch-all that preserves information about something unexpected happening, even when the firmware cannot name the exact cause. In most cases, the error is transient and triggered by a firmware bug that has since been fixed in a later release.

Step-by-Step Fix

1. Note the full error code displayed on screen. Write down or photograph the complete error code, including any additional hex values shown below the main code. This information is essential for Prusa Support to identify the specific firmware condition.
2. Restart the printer. Power off, wait 10 seconds, and power back on. A transient unknown error will not recur after a clean restart.
3. Update firmware to the latest version. Unknown errors frequently correspond to bugs that were identified and fixed after the firmware version you are running was released. Download from prusa3d.com/drivers and install via USB.
4. Note what action triggered the error. If the error appears consistently — for example, always when loading filament, always on a specific print, or always during calibration — document that sequence precisely.
5. Contact Prusa Support with the exact error code and any reproduction steps. Providing both the code and the conditions that trigger it allows Prusa engineers to map the error to an internal fault and provide a fix.

Parts Required

• No replacement parts are typically required for this fix — the issue is almost always firmware-related

If the error is reproducible and a firmware update does not resolve it, contact Prusa Support at help.prusa3d.com with the full error code and detailed reproduction steps.

Frequently asked questions

What does Prusa 13601 mean?

Prusa error 13601 (Unknown Error) appears on the MK4 and its equivalents are #31601 on the CORE One, #35601 on the CORE One L, #26601 on the MK4S, #27601 on the MK3.9S, #21601 on the MK3.9, #28601 on the MK3.5S, #23601 on the MK3.5, #17601 on the XL, and #12601 on the MINI. The firmware encountered an error condition that does not match any defined error code in the current firmware version.

How do I fix Prusa 13601?

Prusa error 13601 is an unclassified firmware error. Learn how to note the code, restart, update firmware, and report the issue to Prusa Support effectively.