Prusa error 13101 (Stuck Filament Detection) appears on the MK4 and is reported as #26101 on the MK4S, #21101 on the MK3.9, #27101 on the MK3.9S, #31101 on the CORE One, #35101 on the CORE One L, and #17108 on the XL. The loadcell sensor measured pressure buildup in the extruder consistent with filament that has become stuck — typically caused by a nozzle clog or excessive resistance in the melt zone.

What the Error Means

The loadcell in MK4-family printers does double duty: it calibrates first-layer height and monitors for stuck filament during printing. When the extruder pushes filament and pressure builds beyond a threshold — indicating the filament cannot advance — the printer halts and raises this error to prevent the motor from grinding filament or damaging the extruder mechanism. Note that a spool tangle will not trigger this error; external tension pulling on the filament above the extruder creates a different force profile than internal pressure from a blocked nozzle.

Step-by-Step Fix

1. Unload filament when prompted. When the error appears on screen, press Unload. The printer will automatically retract the filament, pause, and prompt you to reload. After reloading, it will attempt to resume the print. This one-step recovery works for isolated incidents.
2. Check for a nozzle clog. If the detection triggers repeatedly on the same print, inspect the nozzle. Perform a cold pull (also called an atomic pull) by heating the nozzle to printing temperature, then slowly cooling while pulling the filament out by hand. Repeat until the pulled plug comes out clean.
3. Reduce print speed. Open PrusaSlicer and reduce the print speed for the affected profile, or use the Tune menu on the printer LCD during a live print to dial back speed. Slower movement gives the extruder more mechanical advantage and reduces pressure spikes that falsely trigger detection.
4. Lower the nozzle temperature slightly. Reduce the nozzle temperature by 5°C increments. A slightly cooler nozzle can improve retraction reliability and reduce oozing-related partial blockages, though too cold a temperature will cause under-extrusion — find the balance by printing a temperature tower.
5. Reduce the volume of extrusion moves. Avoid long, high-volume extrusion segments where possible. Splitting large solid infill regions into smaller sections (using infill settings in your slicer) reduces the continuous pressure load on the extruder.
6. Disable detection as a last resort. Navigate to LCD Menu → Settings and disable stuck filament detection. This allows printing to continue but removes the safety net — an actual clog will cause filament grinding rather than a clean stop. Use this option only while investigating the root cause, not as a permanent setting.

Parts Required

• No replacement parts are typically required for this fix — basic tools only
• Replacement nozzle (if cold pull reveals a permanently blocked or worn nozzle)

If stuck filament detection triggers on a specific material or print geometry repeatedly even after speed and temperature adjustments, contact Prusa Support for guidance on extruder calibration or hardware inspection.

Frequently asked questions

What does Prusa 13101 mean?

Prusa error 13101 (Stuck Filament Detection) appears on the MK4 and is reported as #26101 on the MK4S, #21101 on the MK3.9, #27101 on the MK3.9S, #31101 on the CORE One, #35101 on the CORE One L, and #17108 on the XL. The loadcell sensor measured pressure buildup in the extruder consistent with filament that has become stuck — typically caused by a nozzle clog or excessive resistance in the melt zone.

How do I fix Prusa 13101?

Prusa error 13101 means the loadcell detected pressure buildup from a stuck or clogged filament. Learn how to unload, clear clogs, and adjust print settings.