Prusa error 13533 (ESP Not Connected) appears on the MK4 and its equivalents are #31533 on the CORE One, #35533 on the CORE One L, #26533 on the MK4S, #27533 on the MK3.9S, #21533 on the MK3.9, #28533 on the MK3.5S, and #23533 on the MK3.5. The Buddy board attempted to communicate with the ESP32 Wi-Fi module during startup but received no response, indicating the module is absent, disconnected, or completely unresponsive.

What the Error Means

Unlike error 13505 (ESP Init, where the module exists but fails to initialize), error 13533 indicates the Buddy board cannot detect the ESP32 module at all — it is as if the module is not there. This typically means the ESP32 module connector on the xBuddy board is loose or has come unplugged, the module has been physically dislodged, or the module has failed completely. The printer will function normally for local USB printing, but all Prusa Connect and remote monitoring features will be unavailable until the module is reconnected or replaced.

Step-by-Step Fix

1. Restart the printer. Some boot-time ESP detection failures are timing-related and clear on the next power cycle. Power off, wait 10 seconds, and power back on.
2. Check the ESP module connector on the xBuddy board. With the printer powered off, open the electronics enclosure. Locate the ESP32 module — it is a rectangular board plugged into a header or socket on the xBuddy board. Confirm it is fully seated and not tilted. Press it firmly into the socket.
3. Inspect for bent pins on the module or socket. Examine both the module’s pin row and the board-side header for any bent or missing pins that could prevent contact.
4. Update firmware. ESP module detection logic is sometimes improved in firmware updates. Download the latest from prusa3d.com/drivers and install via USB. A firmware update also refreshes the ESP32 firmware.
5. Contact Prusa Support with photos of the ESP connector area. If the module is properly seated and the error persists, the module or its xBuddy board socket may be damaged. Photos help support triage the issue remotely.

Parts Required

• Replacement ESP32 Wi-Fi module (if the module has failed or pins are damaged — contact Prusa Support first)

If the module connector is undamaged and properly seated but the printer still cannot detect it, contact Prusa Support at help.prusa3d.com for replacement guidance.

Frequently asked questions

What does Prusa 13533 mean?

Prusa error 13533 (ESP Not Connected) appears on the MK4 and its equivalents are #31533 on the CORE One, #35533 on the CORE One L, #26533 on the MK4S, #27533 on the MK3.9S, #21533 on the MK3.9, #28533 on the MK3.5S, and #23533 on the MK3.5. The Buddy board attempted to communicate with the ESP32 Wi-Fi module during startup but received no response, indicating the module is absent, disconnected, or completely unresponsive.

How do I fix Prusa 13533?

Prusa error 13533 means the ESP32 Wi-Fi module is not detected by the Buddy board. Learn how to reseat the module connector and update firmware to restore Wi-Fi connectivity.