Seat Belt Tensioner: Description and Operation

The front passenger seat is equipped with a pyrotechnic seat belt tensioner. In the event of frontal impact at a road speed above approx. 11 mph, the Supplemental Restraint System (SRS) control module causes the igniter in the gas generator of the pyrotechnic seatbelt tensioner to be activated. This drives the piston (3) downward in the cylinder and tensions the seat belt via a cable (2). Thus the passenger is held tightly against the backrest.