Preheat the hotend to 80°C through the Settings/Temperature menu of your printer.

Once the hotend temperature reach 80°C, unplug the hotend fan connector.

After few seconds you should get the Err: EXTR. FAN ERROR error message displayed on the printer.

Set targeted temperatures back to 0°C via Preheat/Cooldown or Settings/Temperature menu.

Quickly plug back the hotend fan and let the hotend cool down under 50°C.

Turn the printer off after hotend and heated bed are cooled down.

If this step behaves differently please verify your connection and firmware. If it continues stop using your printer and contact us or ask for help.