Hyundai Elantra MD/UD: Seat Belt Pretensioner (BPT). Description 
and Operation - Seat Belt Pretensioner - Restraint - Hyundai Elantra MD 2010-2015 Service manualHyundai Elantra MD/UD: Seat Belt Pretensioner (BPT). Description and Operation

Description

The Seat Belt Pretensioners (BPT) are installed inside Center Pillar (LH & RH). When a vehicle crashes with a certain degree of frontal impact, the pretensioner seat belt helps to reduce the severity of injury to the front seat occupants by retracting the seat belt webbing. This prevents the front occupants from thrusting forward and hitting the steering wheel or the instrument panel when the vehicle crashes.
Never attempt to measure the circuit resistance of the Seat Belt Pretensioner (BPT) even if you are using the specified tester. If the circuit resistance is measured with a tester, the pretensioner will be ignited accidentally. This will result in serious personal injury.