Prusa MK4 Error Code 19: How to Fix It

Q: What does Error Code 19 mean on a Prusa MK4?

Error Code 19 on the Prusa MK4 means the printer's automatic belt tension measurement has detected that the X-axis or Y-axis belt is outside the acceptable tension range — either too loose or too tight. The MK4 uses an input shaper accelerometer to measure belt resonance and calculate tension, so it can catch issues that would be invisible to a visual check alone.

Q: How tight should the belts be on a Prusa MK4?

Prusa targets a belt tension value shown in the Belt Status menu, typically in a range around 240–300 (the exact displayed unit is an internal score, not Newtons). The printer guides you with on-screen indicators showing acceptable and out-of-range zones. As a rough physical check, a properly tensioned MK4 belt should feel firm with very little sag — roughly like a guitar string that gives a low-pitched pluck.

Q: Can I keep printing with Error Code 19?

It is not recommended. A belt that is too loose will cause layer shifting and ringing artifacts in prints. A belt that is too tight accelerates wear on motor bearings, idler bearings, and frame components. For anything beyond a quick test print, resolve Error Code 19 before continuing to use the printer.

Q: How often do Prusa MK4 belts need to be replaced?

With normal use, Prusa MK4 belts can last thousands of print hours before needing replacement. Belts are more likely to require attention after a crash, if the printer is moved frequently, or if filament debris accumulates on the pulleys. Regularly checking belt tension every few months and keeping pulleys clean will maximize belt lifespan.

Q: Why does my MK4 keep showing Error Code 19 after I adjust the belt?

If belt tension errors persist after adjustment, check for: a worn or slipping pulley set screw (the pulley may be loose on the motor shaft), a seized or wobbling idler bearing that causes inconsistent tension readings, a damaged belt with internal cord breakage that stretches unevenly, or a firmware issue causing the input shaper sensor to misreport. Try replacing the belt first, and if the error continues, update firmware and contact Prusa Support.

Abstract

Error Code 19 on the Prusa MK4 means the printer has detected that one or both of its drive belts — the X-axis or Y-axis belt — is either too loose or too tight, falling outside the acceptable tension range. The MK4 measures belt tension automatically using its input shaper sensor, so even a small shift can trigger this warning. Left unaddressed, incorrect belt tension leads to print quality problems like ringing, layer shifting, or failed prints.