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Selftest failed (MINI/MINI+)

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Last updated a year ago
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The selftest verifies the most important components of the printer. It is the first part of the wizard, which will start when you turn on the printer for the first time, or you can start it from LCD Menu -> Calibration -> Selftest.

Each part of the test can also be run individually from LCD Menu -> Calibration -> Test FANs / Test XYZ-axis / Test heaters. You can always check the results of the previously completed selftest from LCD Menu - Calibration - Show selftest results.

These instructions are for firmware version 4.3.0 and above. Make sure your firmware is up to date.

What it tests

  • Hotend Fan
  • Print fan
  • X-axis
  • Y-axis
  • Z-axis
  • Hotend (nozzle) heater
  • Heatbed heater

Pay close attention to both the printer and the LCD display. A green checkmark () should appear by the part being tested. If all is green you are good to go.

With the exception of the heaters, a red X will appear next to the tested component if it fails. Make a note of where it failed and let the self-test complete. If anything does not check out, it will produce the message:

"The self-test failed to finish. Double-check the printer's wiring and axes".

If a heater (hotend or heatbed) will fail the selftest, the printer will, for safety reasons, reboot and produce an error screen. If the magnetic flexible steel sheet is not on the machine it will fail the Selftest when checking the hotend and bed heater. For more details of how each component is tested, please see the Github release notes.

Troubleshoot a failed component


Verify if there is nothing blocking the rotation of the fans - Debris might get between the blades. Bigger parts can be cleared with tweezers, and dust can be cleared with a computer cleaner spray.

Hold the fan with your hand while using the compressed air otherwise, you might damage the blades.


  • Move the axes by hand to make sure there is nothing hindering their path.
  • Make sure that the belt pulleys are secured on the Y- and X-motor shaft. One of the set-screws must be firmly tightened over the flat part of the motor shaft.
  • Check if the belts aren't extremely loose, as they might skip on the teeth of the belt-pulley.
  • Try to clean, then apply lubricant to the smooth rods.
  • If a failure happens on the Z-axis, it could indicate a problem with the M.I.N.D.A./SuperPINDA sensor.


  • Make sure the flexible steel sheet is on the bed.
  • Make sure the ambient temperature is above 18 °C.
  • Make sure the printer is not standing in a draft or close to an air condition unit.

In case of issues with either heater (bed/hotend), a red error screen will fill the LCD display, showing the error and a QR-code which will link you to an article for troubleshooting the component. In case this happens, check the wiring on the Buddy board.

Before checking the wiring, make sure you turn off and unplug the power!

Open the electronics box by the screw in the printed cable cover. Check if all of the cables are well connected. In case you find any loose connections, plug it back in and make sure you feel/hear the safety-latch lock into place. After that, close the box, turn the printer back on, and restart the Selftest or Wizard in the Calibration Menu.

Make sure you have checked your wiring before contacting support. It is crucial for further investigation.

Saving the Selftest results

This is a feature for advanced users.

Starting from firmware version 4.3.2, if you have a USB drive (FAT32) connected to the MINI/+ when performing the Selftest, the printer will save three logfiles into the drive as a text file. In the files, you can see the results for the tests on the two fans, the two heaters, and the three axes.

These files might be used for troubleshooting any selftest issues which have not been resolved through normal troubleshooting.

Your printer's serial number is contained in each file. It is recommended to remove the serial number from the file before sharing them publicly.


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