Safety & assistance

Seat-belt pretensioner

Removes belt slack during defined safety events.

Where it sits

In a buckle, retractor or belt anchorage according to design.

How it works

A triggered mechanism tightens the restraint path under controller command.

Think of it as

A fast emergency take-up mechanism for the belt.

Symptoms when it fails

A restraint fault or crash history needs the prescribed inspection and replacement procedure.

Lifespan

Inspect and service using model-specific guidance, especially after a collision; warning lights require diagnosis.

Repair cost

Calibration, matched modules and post-collision work may dominate cost. An illuminated warning does not identify a replaceable part.

The BMW angle

A deployed BMW pretensioner is not repaired by clearing a fault code.

Used in

BMW safety systems according to market, model year and option package.

Sources
Same system

Safety & assistance