A pretensioner is a device that is connected to the safety belt buckle, safety belt retractor or/and outboard lower safety belt anchor assembly. The pretensioner tightens the seat belt during certain crashes. Pretensioners may deploy with or without airbag deployment. Depending upon the vehicle, pretensioners may activate in certain frontal, side, rear and/or rollover crashes. For some vehicles, pretensioners will deploy if the safety belt is buckled.
The buckle pretensioner uses a pyrotechnic gas generator to propel a piston that is attached to the safety belt buckle with a cable. The cable pulls the buckle down toward the seat tightening the belt.
The anchor pretensioner uses a pyrotechnic gas generator to propel a piston that is attached to the outboard lower safety belt anchor assembly with a cable. The cable pulls the anchor assembly down toward the floor tightening the belt.
The retractor pretensioner uses a pyrotechnic device that “backwinds” the retractor spool tightening the belt.
Use the same precautions you would for the other SRS inflatable restraint components. There may be power to activate a pretensioner for a short time after the battery is disconnected or the ignition is turned off.