Prusa error 13301 (Homing Error Z) appears on the MK4 and its equivalents are #26301 on the MK4S and #21301 on the MK3.9. The Z-axis homing sequence failed — the printer attempted to establish Z-zero using the loadcell probe method but could not complete it within the expected parameters.

What the Error Means

MK4-family printers home the Z axis by pressing the nozzle lightly against the print surface and detecting the contact force via the loadcell sensor. This replaces the traditional optical or mechanical end-stop approach. The homing sequence fails when the loadcell cannot reliably detect nozzle contact — typically because a ball of hardened filament on the nozzle tip is absorbing the contact force and creating a false offset, because the steel sheet is not properly seated on the magnetic bed, or because there is a mechanical obstruction preventing the nozzle from actually reaching the bed surface.

Step-by-Step Fix

1. Confirm the steel sheet is properly seated. The PEI steel sheet must lie flat on the heated magnetic bed with no lifted corners or debris underneath. Remove and re-seat the sheet before retrying.
2. Clean the nozzle tip. Heat the nozzle to printing temperature (for example 210°C for PLA) and wipe the tip clean with a brass brush or heat-resistant cloth. Even a small bead of cooled filament on the tip can interfere with loadcell contact detection.
3. Run First Layer Calibration. Navigate to LCD Menu → Calibrations & tests → First Layer Calibration to trigger a fresh homing and probing sequence with visual feedback.
4. Check for mechanical obstructions along the Z axis. Confirm nothing is sitting on the print surface and that the X-axis gantry is free to move — look for wiring that may have been accidentally routed across the bed.
5. Run the Loadcell test from the calibrations menu. LCD Menu → Calibrations & tests → Loadcell test will check sensor function in isolation and report if the loadcell response is abnormal.
6. Inspect loadcell wiring. With the printer powered off, check the loadcell cable connector at the Nextruder and at the xBuddy board for looseness.

Parts Required

• No replacement parts are typically required for this fix — basic tools only
• Replacement loadcell (if Loadcell test reports a sensor failure — consult Prusa Support)

If homing errors persist after cleaning the nozzle and verifying the loadcell, contact Prusa Support at help.prusa3d.com with the results of the Loadcell test.

Frequently asked questions

What does Prusa 13301 mean?

Prusa error 13301 (Homing Error Z) appears on the MK4 and its equivalents are #26301 on the MK4S and #21301 on the MK3.9. The Z-axis homing sequence failed — the printer attempted to establish Z-zero using the loadcell probe method but could not complete it within the expected parameters.

How do I fix Prusa 13301?

Prusa error 13301 means Z-axis homing failed. Learn how to check the loadcell, clean the nozzle, and clear mechanical obstructions to restore reliable homing.