Emergency Tensioning Devices, belt force limiters

The front seat belts and the outer seat belts in the rear are equipped with ETDs and seat belt force limiters.

The ETDs tighten the seat belts in an accident, pulling them close against the body.

The ETDs do not correct incorrect seat positions or incorrectly fastened seat belts.

The ETDs do not pull vehicle occupants back towards the backrest.

Seat belt force limiters, when triggered, help to reduce the peak force exerted by the seat belt on the vehicle occupant.

The seat belt force limiters for the front seats are synchronized with the front air bags. These take on a part of the deceleration force. Thus, the force exerted on the occupant is distributed over a greater area.

The ETDs can only be activated when:

  • the ignition is switched on.
  • the restraint systems are operational; see "SRS warning lamp" ().
  • the belt tongue is engaged in the buckle on each of the lap-shoulder belts in the front.
  • the front-passenger seat is occupied and the belt tongue is engaged in the buckle on the front-passenger side.

The ETDs on the outside seats in the rear compartment are triggered independently of the lock status of the seat belts.

The ETDs are triggered depending on the type and severity of an accident:

  • if, in the event of a head-on or rear-end collision, the vehicle decelerates or accelerates rapidly in a longitudinal direction during the initial stages of the impact
  • if, in the event of a side impact, on the side opposite the impact the vehicle decelerates or accelerates rapidly in a lateral direction
  • if, in certain situations where the vehicle overturns, the system determines that it can provide additional protection

If the air bags are deployed, you will hear a bang, and a small amount of powder may also be released. Only in rare cases will the bang affect your hearing. The powder that is released generally does not constitute a health hazard. The WARNING SRS warning lamp lights up.


Pyrotechnic ETDs that were activated must be replaced.

For your safety, when disposing of the pyrotechnic ETDs always follow our safety instructions. These are available at any authorized Mercedes-Benz Center.

in the buckle on the frontpassenger seat. Otherwise, the Emergency Tensioning Device If the front-passenger seat is not occupied, do not engage the seat belt tongue in the buckle on the frontpassenger seat. Otherwise, the Emergency Tensioning Device could be triggered in the event of an accident.

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