Hi Reezo,
Which ecu's you can check depends on your software (or app on iPhone for example).
In my case, I used an iCarsoft BMM v2.0 that is able to read the A/C system and I got an error: 8011B5.
I did however take of the A/C control unit a while ago for a retrofit. Might have to do something with that.
My car will have an A/C service tomorrow so I'm wondering how much gas was left in the system, as this can also tell a lot
Cheers