Seat Belt TENSIONERS
WARNING: This page does not describe the selected car, but rather 151 other vehicles, including the 2006 BMW X5, 2006 BMW M3, 2006 BMW 330Ci, 2006 BMW 325Ci, and 2005 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.
Pyrotechnic seat belt tensioners are used as a method of reducing the spooling effect of the seat belts during a collision.
The seat belt latch is connected to the pyrotechnic device through a cable. The control module is responsible for triggering the belt tensioner based on its programmed parameters.
The pyrotechnic device is similar to an airbag assembly in that when the control module triggers the belt tensioner, a small gas charge is ignited in the tensioner assembly and the pressure forces the cable to pull the latch tight.