could be side airbags or seatbelt pre tensioners, either way they are very unreliable. Id try pulling the connector apart and reseating it first see what happens, ignition off of course.
If any part of the airbag system is tampered with - including disconnection - a fault code will be shown. This may self clear, but for sure in VAG's and some Mercs it doesn't.
Can't comment for Nissan!
John