Prusa MK4 Error Code 18: How to Fix It
Medium 20-60 minutes Medium Severity
Verified June 2026
- Error Code
- 18
- Brand
- Prusa
- Product Type
- 3d_printer
- Severity
- Medium
- DIY Difficulty
- Medium
- Estimated Fix Time
- 20-60 minutes
Ad
Tools You'll Need
- Isopropyl alcohol (90% or higher)
- Lint-free cloth or paper towel
- Soft brass brush or nozzle cleaning tool
- Heat-resistant gloves
- USB drive (for firmware update)
- Phillips screwdriver (for Nextruder disassembly if needed)
- T10 Torx screwdriver (for Nextruder housing screws if needed)
How to Fix Error Code 18
-
Restart the Printer
-
Update Printer Firmware
Do not power off the printer during a firmware update, as this can corrupt firmware and require a factory reset. -
Check for Debris or Filament on the Nozzle and Bed
The nozzle is hot during cleaning. Use heat-resistant gloves or only touch approved surfaces. Keep flammable materials away. -
Inspect the Loadcell Wiring and Cable Connections
Always unplug the printer from mains power before inspecting internal wiring to avoid electric shock. -
Re-run the Full Loadcell Calibration Routine
Do not tap or bump the printer frame during calibration. External vibrations will corrupt the sensor zero-point reading. -
Check and Reseat the Nextruder Loadcell Sensor
Unplug the printer from mains power before disassembling the printhead. Take note of cable routing before removal so nothing is incorrectly routed on reassembly. -
Perform a Factory Reset (Last Resort Software Fix)
A factory reset deletes all saved settings. Write down any custom values (e-steps, flow rate, etc.) before proceeding.
Parts You May Need
Nextruder loadcell sensor
Check Price on Amazon
Nextruder cable harness
Check Price on Amazon
Nextruder loadcell sensor
Check Price on Amazon
Nextruder cable harness
Check Price on Amazon
Nextruder loadcell sensor
Check Price on Amazon
Nextruder cable harness
Check Price on Amazon
Ad
When to Call a Professional
If you have replaced the loadcell sensor, verified all wiring is intact, updated to the latest firmware, and performed a factory reset — and Error Code 18 still appears — the fault likely lies with the loadcell sensor itself being defective, or a failure on the xBuddy or Loveboard electronics that process the sensor signal. At this point, contact Prusa Research support directly at help.prusa3d.com and provide your printer's serial number and a description of steps already taken. If your printer is under warranty, Prusa may ship a replacement loadcell or board. Attempting to repair main electronics boards without electronics experience risks permanent damage.Frequently Asked Questions
What does Error Code 18 mean on a Prusa MK4?
Error Code 18 on the Prusa MK4 means the loadcell calibration has failed. The loadcell is a force sensor in the Nextruder printhead that measures pressure during bed leveling and filament loading. When calibration fails, the printer cannot safely determine nozzle-to-bed distance and stops to prevent a crash.
Can I print with a Prusa MK4 showing Error 18?
No, you should not attempt to print while Error 18 is active. The loadcell is critical for first-layer mesh bed leveling and filament detection. Printing without a functioning loadcell can result in the nozzle crashing into the bed, ruining the print surface, and potentially damaging the printhead.
Does vibration cause Prusa MK4 loadcell calibration to fail?
Yes. The loadcell calibration process requires the printer to detect very small force changes, and any external vibration — such as bumping the table, nearby machinery, or even a washing machine running in the same room — can corrupt the baseline reading and trigger Error 18. Always calibrate on a solid, stable surface away from vibration sources.
How do I update Prusa MK4 firmware to fix Error 18?
Download the latest firmware (.bbf file) from prusa3d.com/drivers. Copy it to the root directory of a FAT32-formatted USB drive. Insert the drive into the MK4's USB port while the printer is off. Power on the printer — it will detect the firmware file and prompt you to update. Follow the on-screen steps and do not power off during the process.
Do I need to replace the loadcell sensor if I keep getting Error 18?
Not necessarily. Error 18 is most often caused by dirty nozzles, loose wiring connectors, firmware bugs, or calibration interference. Only consider replacing the loadcell sensor after you have cleaned the nozzle, reseated all cables, updated firmware, and done a factory reset without success. If the sensor must be replaced, order the correct Nextruder loadcell replacement part from Prusa's official spare parts store.