CAN Bus Seat Mii: Read Error Codes.

Hi, I would like to read the SRS/airbag error code for a Seat Mii 1.0 from 2012.
Based on the wiring diagram, I know that the issue is related to the CAN drive (which I believe is referred to as the CAN motor here).
The wiring diagram also indicates that the diagnostic interface connects all CAN buses to the OBD connector, but using non-standard pins (3 and 11 in this case). When I measure at the corresponding pins, I see that the CAN bus is inactive. Only the CAN used for diagnostics is active.

(1) I think I have two options: either I tell the interface/gateway to release the motor control unit (MCU), or I find a way to inject my own frames into the CAN bus. That should probably be possible with one of the cheaper ELM-based tools, right?
And then I would also need information about the gateway and what codes it requires from me. How can I obtain this information?

However, since I only want to read error codes and don't need to send my own frames for that purpose, there is another option:

(2) Ich gehe hinters Gateway an den CAN Antrieb und Capture alle Frames. Eines davon wird schon das richtige sein, schliesslich wird die Airbagkontrollleuchte aktiviert, was doch bedeutet, es muss vom Airbagmodul ein entsprechendes Frame zum Dashboard geschickt worden sein. Or what?

Best regards,

It's easier to buy a diagnostic system and see what's happening in the background.