Mercedes Benz 2009 M-Class User Manual

Depending on vehicle production date, the 
seat belts for the front and rear or rear 
outer seats are equipped with emergency 
tensioning devices and belt force limiters.

The ETD is designed to activate in the 
following cases:

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in frontal or rear-end impacts 
exceeding the system deployment 
threshold

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in certain vehicle rollovers

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if the restraint systems are operational 
and functioning correctly, see 
1 indicator lamp (

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page 423)

In an impact, emergency tensioning 
devices remove slack from the belts in 
such a way that the seat belts fit more 
snugly against the body. Belt force limiters, 
when activated, are employed to help 
reduce the peak force exerted by the seat 
belts on occupants during a crash.

The active head restraints are intended to 
offer the driver and front passenger 
increased protection from whiplash type 
injuries. In the event of a rear-end collision, 
the active head restraints on the driver’s 
and front passenger’s seats are designed 
to move forward in the direction of travel, 
providing the head with increased support 
earlier on in the collision sequence. The 
active head restraints move forward 
whether the seat is occupied or not.

i

G

A pyrotechnic emergency tensioning device 

(ETD) that was activated must be replaced.

When disposing of the pyrotechnic emer-

gency tensioning device, our safety instruc-

tions must be followed. These are available 

at your authorized Mercedes-Benz Light 

Truck Center.

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Only use seat or head restraint covers which 

have been tested and approved by 

Mercedes-Benz for your vehicle model. 

Using other seat or head restraint covers 

may interfere with or prevent the activation 

of the active head restraint. Contact an 

authorized Mercedes-Benz Light Truck 

Center for availability.