Possible Causes

WARNING: This page is about a different car, the 2009 Mazda 6. However, it is still accessible from the selected car via links, so may be relevant.

Passenger-side air bag module (inflator No. 1) connector malfunction
Open or short circuit or short to ground or short to power supply in the wiring harness between the passenger-side air bag module (inflator No. 1) and the SAS control module.
Passenger-side air bag module (inflator No. 1) malfunction
SAS control module malfunction