Prusa MMU3 Error Code 13: How to Fix It

Q: What does Error Code 13 mean on the Prusa MMU3?

Error Code 13 on the Prusa MMU3 means a stepper motor has stalled — it attempted to move but was unable to complete its motion. This is most commonly caused by a filament jam, mechanical binding in the selector or idler, a loose motor connector, or a worn drive gear.

Q: Which motor is stalling when I get MMU3 Error 13?

Error Code 13 can refer to any one of the MMU3's motors (selector, idler, or one of the five filament pulley motors). Run the MMU3 self-test from the printer LCD menu to identify exactly which motor is responsible. The self-test will cycle each motor individually and flag the failing one.

Q: Can a filament jam cause Prusa MMU3 Error Code 13?

Yes — a filament jam is one of the most common causes of Error Code 13. When filament is stuck in a PTFE tube, a channel, or around the drive gears, the motor hits resistance it cannot overcome and stalls. Always clear any filament jams first before investigating electrical or mechanical causes.

Q: How do I prevent Prusa MMU3 motor stalling from happening again?

Regular maintenance is the best prevention. Keep PTFE tubes clean and replace them if they are kinked or yellowed, lubricate the selector rails and idler shaft every few months, store filament in dry conditions to prevent brittle breakage inside the unit, and keep your MMU3 firmware up to date. Also ensure filament spool holders allow spools to unwind freely without binding.

Q: Is it safe to keep printing if I dismiss Prusa MMU3 Error 13?

No — you should not continue printing while Error Code 13 is active. A stalling motor means the MMU3 cannot reliably load or unload filament, which will result in failed prints, filament grinding, and potential damage to the drive gears or motor. Resolve the underlying cause before resuming printing.

Abstract

Prusa MMU3 Error Code 13 indicates that one of the stepper motors inside your Multi Material Upgrade unit has stalled — meaning it stopped moving when it was supposed to. This typically happens because of a filament jam, mechanical obstruction, loose wiring, or a motor that is underpowered or failing. Catching and fixing this error promptly will prevent print failures and potential damage to your MMU3 unit.