Hi everyone, I'm new to this forum but just bought an Audi a3 2011 last week and it had one of the mirrors damaged and had to replace it. I replaced the mirror, complicated job to be honest with taking the door frame out and everything else and when I put everything back together the Passenger Airbag Light came on. I took the door frame apart again and checked if everything is plugged properly and seems to be no issue however the light is still on. The car did not had this issue before so maybe a faulty sensor or something else? Any ideas?

You need a code reader to see what it flags up... you really can't do much to these cars without a code reader.

It would be a heck of a co-incidence if the airbag sensor failed just when you removed the door panel. It's more likely I suggest that you have dislodged a plug connector or broken a wire.