Prusa error 13305 (Homing Error Y) appears on the MK4 and is reported as #26305 on the MK4S, #21305 on the MK3.9, and #23305 on the MK3.5. The printer attempted to home the Y-axis and the motion system did not complete the sequence within the expected position limits.

What the Error Means

Y-axis homing moves the print bed to its reference position by driving the motor until the axis reaches a physical stop. If the firmware does not detect the expected feedback — or the bed travels beyond its allowed range — it reports a homing failure. This error typically points to a mechanical problem: an obstruction blocking bed travel, a belt that is too loose or too tight, a motor pulley that has slipped on the shaft, or bearings that are positioned incorrectly and creating friction or binding. An unplugged Y-axis motor connector is also a straightforward cause to rule out first.

Step-by-Step Fix

1. Remove debris from the belt and smooth rods. Inspect the area under the print bed for filament strands, dust clumps, or any object that could block bed movement. Check both smooth rods along the Y-axis and the belt path for anything caught between components.
2. Inspect and adjust Y-axis belt tension. With the printer off, push and release the print bed by hand across the full Y range. It should move smoothly with firm, consistent resistance. A slack belt will skip teeth under load; an over-tight belt creates excess friction. Adjust the belt tensioner until the belt produces a low, consistent tone when plucked — similar to a guitar’s low E string.
3. Check the motor pulley alignment. The motor pulley set screw must bear against the flat face of the motor shaft. Verify the set screw is tightened onto the flat, not on the round portion of the shaft. Also confirm there is correct spacing between the face of the pulley and the motor body — the pulley should not rub the motor housing or sit too far out.
4. Verify bearing placement. On single-bearing setups, the bearing should be centered in its carrier. On dual-bearing setups, the two bearings should be positioned near the center of the Y-carriage without touching the edges of the pocket — contact at the pocket edges creates binding that mimics motor failure.
5. Check the Y-axis motor connector inside the xBuddy box. Open the electronics enclosure and verify the Y motor cable is fully seated at the board connector. A partially inserted connector produces unpredictable motor behavior that can cause homing to fail.

Parts Required

• No replacement parts are typically required for this fix — basic tools only
• Replacement Y-axis belt (if the belt is visibly frayed or has a damaged tooth)
• Replacement LM8UU bearings (if bearings are worn and creating drag)

If the axis moves freely by hand and all connections are secure but the error persists, contact Prusa Support for further motor or board-level diagnosis.

Frequently asked questions

What does Prusa 13305 mean?

Prusa error 13305 (Homing Error Y) appears on the MK4 and is reported as #26305 on the MK4S, #21305 on the MK3.9, and #23305 on the MK3.5. The printer attempted to home the Y-axis and the motion system did not complete the sequence within the expected position limits.

How do I fix Prusa 13305?

Prusa error 13305 means Y-axis homing failed. Fix belt tension, motor pulley alignment, bearing placement, and debris issues on MK4, MK4S, MK3.9, MK3.5.