Service Reset (resetting maintenance) on the FB Mondial SMX 125i is performed by unlocking the ignition switch, holding down the function button on the right side of the display for at least 5 seconds, and then turning on the ignition while the button is held down.
After a short time, the "Code" appears on the display, and in the three-digit display, you select "211". The selection and confirmation are also done with the function button.
The maintenance indicator on the display is now reset.
OBD can be accessed via the OBDII protocol at the engine control unit for this vehicle, for example, using:
https://shop.dieselschrauber.org/en/obd2-diagnose-kit-p-321.php