Prusa error 13304 (Homing Error X) appears on the MK4 and its equivalents are #26304 on the MK4S, #27304 on the MK3.9S, #21304 on the MK3.9, #28304 on the MK3.5S, and #23304 on the MK3.5. The printer attempted to home the X axis but the carriage did not trigger the end-stop within the expected travel distance, indicating a mechanical or electrical fault preventing reliable homing.

What the Error Means

X-axis homing drives the carriage toward the end-stop (either a physical switch or hall-effect sensor depending on the model) and expects to detect the trigger within the full X travel range. If the trigger is never detected, the firmware raises this error. Common causes include a loose or slipping motor pulley that allows the motor to turn without the belt actually moving the carriage, belt tension that is too low to transmit motion reliably, a physical obstruction on the X axis such as a print left on the bed or wiring catching on the carriage, or a disconnected end-stop or hall sensor connector.

Step-by-Step Fix

1. Remove any objects from the print surface. A failed print or tool left on the bed can block carriage movement. Clear the surface before retrying.
2. Check for wiring obstructions. Ensure the cable bundle that runs with the X carriage is not catching on the gantry or printer frame during full-range motion.
3. Assess X-axis belt tension. Pluck the belt and listen for a low-pitched twang — a properly tensioned belt should produce a clear tone, not a dull thud. Tighten the belt via the tensioner on the X carriage if it feels slack.
4. Inspect the X end-stop or hall sensor connector. Follow the end-stop wire to its connector on the xBuddy board and confirm it is fully seated. On hall-effect sensor models, check both the connector and that the sensor cable is not damaged.
5. Check motor pulley grub screws. With the printer powered off, try to wiggle the motor pulley on the X motor shaft. If it moves relative to the shaft, tighten both grub screws — the flat-sided grub screw must seat on the motor shaft flat.
6. Manually move the X carriage. Push the carriage slowly along the full X travel by hand with the printer off. It should glide smoothly without sticking or grinding. Rough spots indicate a bearing or rod issue that needs cleaning or lubrication.

Parts Required

• No replacement parts are typically required for this fix — basic tools only
• Replacement X-axis belt (if belt is cracked or has teeth missing)
• Replacement X end-stop switch or hall sensor (if confirmed faulty)

If homing continues to fail after checking belts, pulleys, and the end-stop, contact Prusa Support at help.prusa3d.com for further diagnosis.

Frequently asked questions

What does Prusa 13304 mean?

Prusa error 13304 (Homing Error X) appears on the MK4 and its equivalents are #26304 on the MK4S, #27304 on the MK3.9S, #21304 on the MK3.9, #28304 on the MK3.5S, and #23304 on the MK3.5. The printer attempted to home the X axis but the carriage did not trigger the end-stop within the expected travel distance, indicating a mechanical or electrical fault preventing reliable homing.

How do I fix Prusa 13304?

Prusa error 13304 means X-axis homing failed. Learn how to check belt tension, end-stop connectors, and axis movement to restore reliable homing on MK4-series printers.