Prusa error 13318 (I2C Receive Undefined) appears on the MK4 and its equivalents are #31318 on the CORE One, #35318 on the CORE One L, #26318 on the MK4S, #27318 on the MK3.9S, #21318 on the MK3.9, #28318 on the MK3.5S, #23318 on the MK3.5, and #12318 on the MINI. An I2C receive operation returned an error condition that does not match any of the defined error categories in the firmware.

What the Error Means

The I2C bus uses a set of defined status codes to indicate the result of each transaction. An I2C Receive Undefined error means the receive operation produced a status code that the firmware does not have a specific handler for — an unexpected bus condition. This can arise from electrical noise on the I2C bus, a transient glitch in a peripheral’s response, or a firmware version where not all hardware-level I2C status codes have been mapped. In practice it behaves similarly to other I2C receive errors: usually transient, resolved by a restart, and only concerning if it recurs consistently.

Step-by-Step Fix

1. Restart the printer. An undefined I2C error on a single occasion is almost always transient and will not repeat after a clean reboot.
2. Power cycle if the restart alone does not clear the error. Disconnect from the wall outlet for 30 seconds before restarting, allowing all residual charge to drain.
3. Update firmware to address potential I2C driver issues. Undefined status codes are often addressed in firmware updates as the firmware team adds explicit handling for previously unmapped conditions. Download the latest release from prusa3d.com/drivers.
4. If the error recurs frequently, inspect the xBuddy board and I2C peripheral connectors. Open the electronics enclosure and check the LCD ribbon cable, accelerometer board connector, and any other I2C peripheral connections. A marginal connection can generate spurious bus states.
5. Contact Prusa Support if the error is reproducible. If you can reliably trigger the error by performing a specific action, document that sequence and contact support.

Parts Required

• No replacement parts are typically required for this fix — basic tools only

If the error is frequent and firmware updates do not resolve it, contact Prusa Support at help.prusa3d.com with your firmware version and a description of when the error appears.

Frequently asked questions

What does Prusa 13318 mean?

Prusa error 13318 (I2C Receive Undefined) appears on the MK4 and its equivalents are #31318 on the CORE One, #35318 on the CORE One L, #26318 on the MK4S, #27318 on the MK3.9S, #21318 on the MK3.9, #28318 on the MK3.5S, #23318 on the MK3.5, and #12318 on the MINI. An I2C receive operation returned an error condition that does not match any of the defined error categories in the firmware.

How do I fix Prusa 13318?

Prusa error 13318 means an undefined I2C receive error occurred on the Buddy board. Learn how to restart, update firmware, and investigate connectors to clear this fault.