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  SRS warning lamp 
lights up.
 SRS warning lamp 
lights up.
WARNING
Pyrotechnic Emergency Tensioning Devices 
that have been deployed must be renewed.
For your safety, when disposing of Emergency 
Tensioning Devices, always observe the 
safety instructions. These are available from 
any authorized Mercedes-Benz Center.
The PRE-SAFE® system has electrically 
operated reversible pre-tensioners that do 
not require replacement after activation.
 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.
 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.
See also:
Important safety notes
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WARNING
The PARKTRONIC is a supplemental system.
It is not intended to, nor does it replace, the 
need for extreme care. The responsibility 
during pa ...
   
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