Theory Of Operation
WARNING: This page is about a different car, the 2020 Jeep Renegade. However, it is still accessible from the selected car via links, so may be relevant.
The location of the anchor buckle tensioner is at the base of the B-pillar. The anchor buckle tensioner is an internal part of the seat belt retractor. When powered, the Occupant Restraint Controller (ORC) sends a test current to the squibs to verify the integrity of the squib and wiring. These circuits are maintained in a "floating" configuration at the ORC (connected to neither power nor ground) as protection against inadvertent deployment.