Prusa error 13505 (ESP Error — WiFi Init) appears on the MK4 and its equivalents span multiple models including the MK4S, MK3.9, MK3.5, and CORE One. The ESP32 Wi-Fi module failed to initialize during startup, which disables Prusa Connect and all remote monitoring functionality until the module recovers.

What the Error Means

The xBuddy board communicates with a dedicated ESP32 microcontroller that handles all Wi-Fi operations. During startup, the Buddy board sends initialization commands to the ESP32 and waits for a ready signal. If the ESP32 does not respond correctly — due to a transient boot-time fault, a firmware incompatibility between the board firmware and the ESP32 firmware, or a loose module connector — the printer logs this ESP init error. The printer can continue to function for local printing from USB even when Wi-Fi is unavailable, so this error does not block all printing activity.

Step-by-Step Fix

1. Restart the printer. Most ESP init errors are one-time boot failures that clear on the next power cycle. Power off, wait 10 seconds, and power back on.
2. Toggle Wi-Fi off and on from the menu. Navigate to LCD Menu → Settings → Network and disable Wi-Fi, then re-enable it. This forces the ESP module to reinitialize without a full printer restart.
3. Check the ESP module connector on the xBuddy board. With the printer powered off, open the electronics enclosure. The ESP32 module plugs into the xBuddy board via a connector — confirm it is fully seated and not tilted in the socket.
4. Update printer firmware to the latest release. ESP module firmware is bundled with the printer firmware. An update will refresh both the Buddy board firmware and the ESP32 firmware, which often resolves compatibility-related init failures. Download from prusa3d.com/drivers.
5. Contact Prusa Support if the module remains unresponsive after a firmware update. Provide the firmware version installed and confirm the ESP connector is seated correctly. The ESP module or xBuddy board may need replacement.

Parts Required

• No replacement parts are typically required for this fix — basic tools only
• Replacement ESP32 Wi-Fi module (if the module is confirmed unresponsive — contact Prusa Support)

If the error persists after updating firmware, contact Prusa Support at help.prusa3d.com for further troubleshooting of the Wi-Fi module.

Frequently asked questions

What does Prusa 13505 mean?

Prusa error 13505 (ESP Error — WiFi Init) appears on the MK4 and its equivalents span multiple models including the MK4S, MK3.9, MK3.5, and CORE One. The ESP32 Wi-Fi module failed to initialize during startup, which disables Prusa Connect and all remote monitoring functionality until the module recovers.

How do I fix Prusa 13505?

Prusa error 13505 means the ESP32 Wi-Fi module failed to initialize. Learn how to restart, toggle Wi-Fi settings, and update firmware to restore network connectivity.