Prusa error 13811 (Crash Recovery Repeated Crash) appears on the MK4 and its equivalents are #31811 on the CORE One, #35811 on the CORE One L, #26811 on the MK4S, #27811 on the MK3.9S, #21811 on the MK3.9, #28811 on the MK3.5S, #23811 on the MK3.5, #17811 on the XL, and #12811 on the MINI. The crash detection system detected multiple collision events during X or Y axis motion — too many to attribute to isolated incidents, indicating an ongoing mechanical problem.

What the Error Means

Prusa’s crash recovery feature detects unexpected motor stalls — moments when the motor receives drive commands but the axis does not move as expected, indicating a physical collision or resistance. A single crash can be recovered from automatically; when crashes repeat within the same print session, the firmware concludes there is a persistent mechanical issue and halts to prevent further damage. The most common mechanical causes are failed print material sitting on the bed obstructing the carriage, insufficient belt tension allowing missed steps to register as crashes, contaminated or insufficiently lubricated motion rails causing drag, and motor pulleys with loose grub screws that slip on the shaft.

Step-by-Step Fix

1. Clear the build plate. Remove any failed print material, supports, or blobs sitting on the bed that could collide with the printhead during X/Y movement. Silicone or PET blobs stuck to the nozzle can also cause false collision detection.
2. Inspect and re-tension X and Y belts. Pluck each belt — it should produce a clear, consistent note. A dull thud indicates a loose belt. Use the belt tensioners on each axis (accessed via calibration menus or by physically adjusting the tensioner idler) to restore correct tension.
3. Clean and lubricate the smooth rods or linear rails. Use a lint-free cloth to wipe down the X and Y smooth rods, removing dust, old grease, and filament debris. Apply a small amount of Prusa’s recommended lubricant (Super-Lube or similar PTFE or lithium-based grease) to the rods and spread it evenly by moving the axis manually.
4. Check motor pulley grub screws. With the printer off, try to rock each motor pulley by hand — X and Y motor pulleys each have two grub screws, and one must seat on the motor shaft flat. If the pulley spins or wobbles relative to the shaft, tighten both grub screws with a 1.5mm hex key.
5. Recalibrate crash sensitivity if the hardware is in good condition. Some firmware versions allow adjusting crash sensitivity in the menu. Reducing sensitivity can prevent false positives from very fast print speeds.

Parts Required

• No replacement parts are typically required for this fix — basic tools only
• Lubricant (Super-Lube or similar PTFE/lithium grease)
• 1.5mm hex key

If crashes persist after checking belts, pulleys, and rails in a clean mechanical state, contact Prusa Support at help.prusa3d.com for further diagnosis.

Frequently asked questions

What does Prusa 13811 mean?

Prusa error 13811 (Crash Recovery Repeated Crash) appears on the MK4 and its equivalents are #31811 on the CORE One, #35811 on the CORE One L, #26811 on the MK4S, #27811 on the MK3.9S, #21811 on the MK3.9, #28811 on the MK3.5S, #23811 on the MK3.5, #17811 on the XL, and #12811 on the MINI. The crash detection system detected multiple collision events during X or Y axis motion — too many to attribute to isolated incidents, indicating an ongoing mechanical problem.

How do I fix Prusa 13811?

Prusa error 13811 means multiple axis collisions were detected during printing. Learn how to clear debris, check belt tension, and lubricate rails to prevent repeated crashes.