Prusa error 13202 (Hotend Preheat Error) appears on the MK4 and surfaces as #26202 on the MK4S, #21202 on the MK3.9, #27202 on the MK3.9S, #31202 on the CORE One, and #35202 on the CORE One L. The firmware detected that the nozzle temperature did not increase by more than 2°C within 20 seconds of starting a preheat cycle.

What the Error Means

At preheat start, the printer checks whether the hotend heater is producing measurable heat. A gain of less than 2°C in 20 seconds indicates a failed or disconnected heater, a faulty thermistor reporting incorrect temperatures, a loose LoveBoard cable connection, or a room temperature below 18°C. On the MK4, MK4S, MK3.9, and MK3.9S, a blown extruder protection fuse on the xBuddy board is also a known cause.

Step-by-Step Fix

1. Power off and let cool. Never work on the hotend while it is at temperature. Wait until the nozzle is below 40°C before touching any cables or components.
2. Verify ambient temperature. The room must be warmer than 18°C. Below that threshold, initial heat rise can be too slow to pass the firmware check.
3. Inspect LoveBoard heater and thermistor cables. Access the LoveBoard — on the MK4/S and MK3.9/S, slide the extruder cover upward; on the CORE One, use a T10 Torx driver to remove the panel. Check that the heater and thermistor cables are fully seated in their connectors with no bent or burnt pins and no visible cable damage.
4. Check the LoveBoard main cable at the xBuddy board. Route the cable visually from the extruder back to the xBuddy board. Look for pinch points where the cable bends sharply, particularly where it exits the extruder housing.
5. Inspect the extruder protection fuse (MK4/S, MK3.9/S). Open the xBuddy box and locate the small fuse on the board. A blown fuse cuts power to the heater entirely. Replace if visually blown or if continuity testing shows an open circuit.
6. Measure heater and thermistor resistance. Use a multimeter to verify heater resistance (typically 14–16 Ω for a 40 W heater) and thermistor resistance (roughly 100 kΩ at room temperature for an NTC 100k). Values outside these ranges indicate a failed component.

Parts Required

• Replacement hotend heater cartridge (if resistance is out of spec)
• Replacement NTC 100k thermistor (if resistance is out of spec)
• Replacement extruder fuse (MK4/S, MK3.9/S — check Prusa’s documentation for the correct rating)
• Digital multimeter
• T10 Torx screwdriver (CORE One)

If the error continues after all checks pass, contact Prusa Support with your resistance measurements for component-level diagnosis.

Frequently asked questions

What does Prusa 13202 mean?

Prusa error 13202 (Hotend Preheat Error) appears on the MK4 and surfaces as #26202 on the MK4S, #21202 on the MK3.9, #27202 on the MK3.9S, #31202 on the CORE One, and #35202 on the CORE One L. The firmware detected that the nozzle temperature did not increase by more than 2°C within 20 seconds of starting a preheat cycle.

How do I fix Prusa 13202?

Prusa error 13202 means the nozzle failed to gain 2°C in 20 seconds. Diagnose heater, thermistor, and LoveBoard connection problems with this guide.