MERCEDES-BENZ B-CLASS 2012 Service Manual

R
Emergency Tensioning Device
for the front
seat belts and the outer seat belts in the
rear
R Seat belt force limiters for the front seat
belts and the outer seat belts in the rear
SRS reduces the risk of occupants coming
into contact with parts of the vehicle's interior
in the event of an accident. It can also reduce
the effect of the forces to which occupants
are subjected during an accident.
SRS warning lamp G
WARNING
The SRS self-check has detected a
malfunction if the 6 SRS indicator lamp:
R does not light up at all
R does not go out after approximately four
seconds after the engine is started
R lights up
after

the engine is started or while
the vehicle is in motion
For your safety, Mercedes-Benz strongly
recommends that you have the system
checked as soon as possible at a qualified
specialist workshop. SRS may otherwise fail
to activate when it is needed in the event of
an accident, which could lead to serious or
fatal injuries. SRS might also be activated
unexpectedly and unnecessarily, which could
also result in injury.
In addition, work carried out improperly on
SRS may render SRS inoperative or cause
unintended air bag deployment. Work on the
SRS system should only be carried out by
qualified specialist personnel. Consult a
qualified specialist workshop.
If it is necessary to modify an air bag system
to accommodate a person with disabilities,
contact an authorized Mercedes-Benz Center
for details. USA only: for further information,
contact our Customer Assistance Center at
1-800-FOR-MERCedes (1-800-367-6372).
The 6 SRS warning lamp in the instrument
cluster lights up when the ignition is switched on. It goes out no later than a few seconds
after the engine is started.
SRS
functions are

checked regularly when the
ignition is switched on or the engine is
running. Therefore, malfunctions can be
detected in good time.
Triggering of Emergency Tensioning
Device and air bags During the first stage of a collision, the air bag
control unit evaluates important physical
data relating to vehicle deceleration or
acceleration, such as:
R
duration
R direction
R magnitude
Based on the evaluation of this data, the air
bag control unit pre-emptively triggers the
Emergency Tensioning Device in the first
stage.
If there is an even higher rate of vehicle
deceleration or acceleration in a longitudinal
direction, the front

air bags are also deployed.
Your vehicle has adaptive, two-stage front air
bags. The air bag control unit evaluates
vehicle deceleration or acceleration in the
event of a collision. In the first deployment
stage, the front air bag is filled with enough
propellant gas to reduce the risk of injuries.
The front air bag is fully deployed if a second
deployment threshold is reached within a few
milliseconds.
The Emergency Tensioning Device and air bag
triggering thresholds are variable and are
adapted to the detected rate of deceleration
or acceleration of the vehicle. This process is
pre-emptive in nature. The triggering process
must take place in good time at the start of
the collision.
The rate of vehicle deceleration or
acceleration and the direction of the force are
essentially determined by:
R the distribution of forces during the
collision
R the collision angle Occupant safety
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R
the deformation characteristics of the
vehicle
R the characteristics of
the object with which
the vehicle has collided
Factors that can only be seen and measured
after a collision has occurred do not play a
decisive role in the deployment of an air bag,
nor do they provide an indication of air bag
deployment.
The vehicle may be deformed significantly,
e.g. the hood or the fender, without an air bag
being deployed. This is the case if only parts
which are relatively easily deformed are
affected and the rate of deceleration is not
high. Conversely, air bags may be deployed
even though the vehicle suffers only minor
deformation. This is the case if, for example,
very rigid vehicle parts such as longitudinal
body members are hit, and sufficient
deceleration occurs as a result.
i The front Emergency Tensioning Devices
can only be triggered if the seat belt
tongues on the front seats are correctly
engaged in the seat belt buckles.
i Not all air bags are deployed in an
accident. The different air bag systems
work independently of each other.
How the air bag system works is
determined by predicting the severity of
the accident, especially vehicle
deceleration or acceleration, and the type
of accident:
R head-on collision
R side impact
R rollover
Safety guidelines for seat belts,
Emergency Tensioning Devices (ETDs)
and air bags G
WARNING
R Damaged seat belts

or seat belts that have
been subjected to stress in an accident
must be replaced. Their anchoring points
must also be checked. Only use seat belts installed or supplied by an authorized
Mercedes-Benz Center.
R Air bags and pyrotechnic Emergency
Tensioning Devices (ETDs) contain
perchlorate material, which may require
special handling and regard for the
environment. Check your

national disposal
guidelines. In California, see
www.dtsc.ca.gov/HazardousWaste/
Perchlorate/index.cfm.
R Air bags and ETDs are designed to function
on a one-time-only basis. An air bag or ETD
that has deployed must be replaced.
R Do not pass seat belts over sharp edges.
They could tear.
R Do not make any modification that could
change the effectiveness of the seat belts.
R Do not bleach or dye seat belts, as this may
severely weaken them. In a crash, they may
not be able to provide adequate protection.
R Do not make any modifications to the SRS
wiring or components.
R Do not modify or remove any components
or parts of the SRS.
R Do not install additional trim material, seat
covers, badges, etc. to the:
-padded steering wheel boss
- knee bag covers
- front-passenger air bag cover
- outer side of front seat bolsters
- outer seat bolsters of the rear bench seat
backrest
- roof frame trim
R Do not install additional electrical/
electronic equipment on or near SRS
components and wiring.
R Keep the area between the air bags and
occupants free of objects (e.g. packages,
handbags, umbrellas etc.).
R Do not hang any objects such as coat
hangers on the coat hooks or the grab
handle above the door. These items may be
thrown around in the vehicle and cause40
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head and other injuries when the window
curtain air bag is deployed.
R Air bag system
components will be hot after
an air bag has inflated. Do not touch them.
R Never rest your feet on the dashboard or
the seat. Always keep both feet on the floor
in front of the seat.
R Improper repair work on the SRS creates a
risk of rendering the SRS inoperative or
causing unintended air bag deployment.
Work on the SRS must therefore only be
performed by qualified technicians.
Consult an authorized Mercedes-Benz
Center.
R For your protection and the protection of
others, when scrapping the air bag unit or
ETD, our safety instructions must be
followed. These are available from any
authorized Mercedes-Benz Center.
R Given the considerable deployment speed,
required inflation volume, and the material
of the air bags, there is the possibility of
abrasions or other, potentially more serious
injuries resulting from air bag deployment.
If you sell your vehicle, Mercedes-Benz
strongly recommends that you inform the
subsequent owner that the vehicle is
equipped with SRS. Also, refer them to the
applicable section in the Operator's Manual. Air bags
Important safety notes G
WARNING
Air bags are designed to reduce the incidence
of injuries and fatalities in certain situations:
R frontal impacts (driver's and front-
passenger front air bags and driver's knee
bag)
R side impacts (side impact air bags and
window curtain air bags)
R rollover (window curtain air bags) However, no system available today can
completely eliminate injuries and fatalities.
When the air bags are deployed, a small
amount of powder is released. The powder
generally does
not
constitute a health hazard
and does not indicate that there is a fire in the
vehicle. In order to prevent potential
breathing difficulties, you should leave the
vehicle as soon as it is safe to do so. If you
have any breathing difficulty but cannot get
out of the vehicle after the air bag inflates,
then get fresh air by opening a window or
door. G
WARNING
In order to reduce the potential danger of
injuries caused during the deployment of the
front air bags, the driver and front passenger
must always be correctly seated and wear
their seat belts.
For maximum protection in the event of a
collision, you must always be in the normal
seat position with your back against the
backrest. Fasten your

seat belt and make sure
that it is correctly positioned on your body.
As the air bag inflates with considerable
speed and force, a proper seating position
and correct positioning of the hands on the
steering wheel will help to keep you at a safe
distance from the air bag. Occupants who are
not wearing their seat belt, are not seated
properly or are too close to the air bag can be
seriously injured or killed by an air bag, as it
inflates with great force instantaneously:
R sit with the seat belt fastened correctly and
in a position that is as upright as possible
with your back against the backrest.
R move the driver's seat as far back as
possible, still permitting proper operation
of vehicle controls. The distance from the
center of the driver's chest to the center of
the air bag cover on the steering wheel
must be at least 10 inches (25 cm). You
should be able to accomplish this by
adjusting the seat and steering wheel. If Occupant safety
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you have any difficulties, please contact an
authorized Mercedes-Benz Center.
R do not lean
your head or chest close to the
steering wheel or dashboard.
R only hold the steering wheel on the outside.
Placing hands and arms inside the rim can
increase the risk and potential severity of
hand/arm injury if the driver front air bag
inflates.
R adjust the front-passenger seat as far back
as possible from the dashboard when the
seat is occupied.
R occupants, especially children, should
never place their bodies or lean their heads
in the area of the door where the side
impact air bag inflates. This could result in
serious or fatal injuries should the side
impact air bag be deployed. Always sit as
upright as possible, wear the seat belt
properly and use an appropriately sized
infant restraint, toddler restraint or booster
seat recommended for the size and weight
of the child.
Failure to follow these instructions can result
in severe injuries to you or other occupants.
If you sell your vehicle, it is important that you
make the buyer aware of this safety
information. Be sure to give the buyer this
Operator's Manual. G
WARNING
Accident research shows that the safest place
for children in

an automobile is in a rear seat.
A side impact air bag related injury may occur
if occupants, especially children, are not
properly seated or restrained when next to a
side impact air bag which needs to deploy
rapidly in a side impact in order to do its job.
To help avoid the possibility of injury, please
follow these guidelines:
(1) Always sit as upright as possible and use the seat belts properly.
Make sure that children 12 years
old and under

use an appropriately
sized child restraint, infant restraint, or booster seat
recommended for the size and
weight of the child.
(2) Always wear seat belts properly.
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 6 SRS warning lamp
lights up.
The air bags are deployed if the air bag control
unit detects the need for deployment. Only in
the event of such a situation will the air bags
provide their supplemental protection.
If the driver and front passenger do not wear
their seat belts, it is not possible for the air
bags to provide their supplemental
protection.
In the event of other types of impacts and
impacts below air bag deployment
thresholds, the air bags will not deploy. The
driver and passenger will then be protected
to the extent possible by a properly fastened
seat belt. A properly fastened seat belt is also
needed to provide the best possible
protection in a rollover.
Air bags provide additional protection; they
are not, however, a substitute for seat belts.
All vehicle occupants must fasten their seat
belts regardless of whether your vehicle is
equipped with air bags or not.
It is important for your safety and that of your
passengers to have deployed air bags
replaced and to have any malfunctioning air
bags repaired. This will help to make sure the
air bags continue to perform their protective
function for the vehicle occupants in the
event of a crash.
Front air bags !
Make sure that there are no objects
exerting force on

the front-passenger seat.
This could cause the system to identify the
seat as being occupied, and in the event of 42
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an accident, the restraint systems on the
front-passenger side might be triggered.
Have triggered
restraint
systems replaced.Driver's air bag
: deploys in front of the
steering wheel; front-passenger front air
bag ; deploys in

front of and above the glove
box.
The front air bags increase protection for the
driver's and front-passenger's head and
chest.
They are deployed:
R at the start of an accident with a high rate
of vehicle acceleration or deceleration in a
longitudinal direction
R in the event of certain frontal impacts
R if the system determines that air bag
deployment can offer additional protection
to that provided by the seat belt
R depending on whether the seat belt is being
used
R independently of other air bags in the
vehicle
If the vehicle rolls over, the front air bags are
generally not deployed.
Front-passenger air bag ; is only activated
if the system determines that the front-
passenger seat is occupied. The 4
PASSENGER AIR BAG OFF indicator lamp on
the center console does not light up
(Y page 53). If a child restraint system is installed on the
front-passenger seat and the PASSENGER
AIR BAG OFF
4 indicator lamp on the
center console is not on:
R a child restraint system without a
transponder for the air bag deactivation
system is installed or
R a child
restraint

system with a transponder
has not been installed properly.
Your vehicle has adaptive, two-stage front air
bags. The air bag control unit evaluates
vehicle deceleration or acceleration in the
event of a collision. In the first deployment
stage, the front air bag is filled with part of the
total available propellant gas, thereby
reducing the risk of injury. If the air bag
control unit recognizes within a few
milliseconds that the vehicle is being braked
or accelerated faster than originally
predicted, the front air bag is filled with the
maximum amount of propellant gas available.
The lighter the passenger-side occupant, the
higher the vehicle deceleration rate required
(predicted at the start of the impact) for
second stage inflation of the front-passenger
front air bag. In the second stage, the front
air bags are inflated with the maximum
amount of propellant gas available.
The front air bags are not deployed in
situations where a low impact severity is
predicted. You will then be protected by the
fastened seat belt.
The front-passenger front air bag will only
deploy if:
R the 45 indicator lamp on the center
console is not lit (Y page 53)
R the air bag control unit predicts a high
impact severity Occupant safety
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Driver's knee bag
Driver's knee bag : deploys under the
steering column. The driver's knee bag is
always deployed
along
with the driver's front
air bag. The driver's knee bag is designed to
operate together with the front air bags in
frontal impacts if certain thresholds are
exceeded. The driver's knee bag operates
best in conjunction with correctly positioned
and fastened seat belts.
Driver's knee bag : increases the driver's
protection against:
R knee injuries
R thigh injuries
R lower leg injuries
Side impact air bags G
WARNING
Only use seat covers which have been tested
and approved by Mercedes-Benz for your
vehicle model. Using other seat covers may
interfere with or prevent the deployment of
the side impact air bags. Contact an
authorized Mercedes-Benz Center for
availability. G
WARNING
The pressure sensors for side impact air bag
control are located in the doors. Do not
modify any components of the doors or door
trim panels including, for example, the
addition of door speakers.
Improper repair work on the doors or the
modification or addition

of components to the doors create a risk of rendering the side
impact air bags inoperative or causing
unintended air bag deployment. Work on the
doors must therefore only be performed by
qualified technicians. Contact an authorized
Mercedes-Benz Center.
Front side impact air bags
: and rear side
impact air bags ; deploy next to the outer
seat cushions.
When deployed,
the

side impact air bags offer
additional protection of the thorax for
occupants on the front seats as well as also
of the pelvis for the vehicle occupants on the
side of the vehicle on which the impact
occurs. However, they do not protect the:
R head
R neck
R arms
The side impact air bags are deployed:
R on the side on which an impact occurs
R at the start of an accident with a high rate
of lateral vehicle deceleration or
acceleration, e.g. in a side impact
R independently of the use of the seat belt
R independently of the front air bags
R independently of the ETDs
If the vehicle rolls over, the side impact air
bags are generally not deployed. Side impact
air bags are deployed if the system detects
high vehicle deceleration or acceleration in a
lateral direction and determines that side
impact air bag deployment can offer 44
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additional protection to that provided by the
seat belt.
Side impact air bags will not deploy in side
impacts which do not exceed the system's
preset deployment thresholds for lateral
acceleration/deceleration. You will then be
protected by the fastened seat belt.
The side impact air bag on the front-
passenger side is not deployed in the
following situations:
R
OCS has detected
that the front-passenger
seat is unoccupied.
R the front-passenger seat belt is not
fastened.
The side impact air bag on the front-
passenger side will deploy if the front-
passenger seat belt is fastened, regardless of
whether the front-passenger seat is occupied
or not.
Window curtain air bags Window curtain air bags
: enhance the
level
of protection for the head, but not chest or
arms, of the vehicle occupants on the side of
the vehicle on which the impact occurs.
Window curtain air bags : are integrated
into the side of the roof frame and deployed
in the area from the A-pillar to the C-pillar.
Window curtain air bags are deployed:
R at the start of an accident with a high rate
of lateral vehicle deceleration or
acceleration, e.g. in a side impact
R on the side on which an impact occurs R
on the driver's side and passenger side, in
the event of a vehicle rollover and if the
system determines
that

air bag deployment
can offer the vehicle occupants additional
protection to that provided by the seat belt
R independently of the use of the seat belt
R regardless of whether the front-passenger
seat is occupied
R independently of the front air bags
Window curtain air bags : will not deploy in
the event of impacts which do not exceed the
system's preset deployment thresholds for
vehicle acceleration/deceleration. You will
then be protected by the fastened seat belt. Seat belts
Important safety notes G
WARNING
Always fasten your seat belt before driving off.
Always make sure all of your passengers are
properly restrained. You

and your passengers
should always wear seat belts.
Failure to wear and properly fasten and
position your seat belt greatly increases your
risk of injuries and their likely severity in an
accident.
If you are ever in an accident, your injuries can
be considerably more severe without your
seat belt properly buckled. Without your seat
belt buckled, you are much more likely to hit
the interior of the vehicle or be ejected from
it. You can be seriously injured or killed.
In the same crash, the possibility of injury or
death is lessened if you are properly wearing
your seat belt. The air bags can only protect
as intended if the occupants are properly
wearing their seat belts. G
WARNING
Never ride in a moving vehicle with the seat
backrest in an

excessively reclined position as
this can be dangerous. You could slide under
the seat belt in a collision. If you slide under Occupant safety
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it, the seat belt would apply force at the
abdomen or neck. That could cause serious
or even fatal injuries. The seat backrest and
seat belt provide the best restraint when the
wearer is in a position that is as upright as
possible and the seat belt is properly
positioned on the body.
G
WARNING
Never let more people ride in the vehicle than
there are seat belts available. Make sure
everyone riding in the vehicle is correctly
restrained with a separate seat belt. Never
use a seat
belt for more than one person at a
time. G
WARNING
Always have damaged seat belts or seat belts
that have been subjected to a load in an
accident replaced and the anchorages
checked.
Only use seat belts that have been approved
by Mercedes-Benz.
Never tamper with seat belts. This can result
in the unintended deployment of the
Emergency Tensioning Devices or the failure
to deploy when necessary.
Do not bleach or dye seat belts, as this may
severely weaken them. In the event of a
collision, they may be unable to provide
adequate protection.
Have all work carried out only by qualified
technicians. Consult a qualified specialist
workshop.
The use of seat belts and infant and child
restraint systems is required by law in:
R all 50 states
R the U.S. territories
R the District of Columbia
R all Canadian provinces
Even where this is not required by law, all
vehicle occupants should correctly fasten
their seat belts before starting the journey. i
See "Children in the vehicle"
(Y page 50) for further information on
infants and children

traveling in the vehicle
as well as on child restraint systems.
Proper use of the seat belts G
WARNING
USE SEAT BELTS PROPERLY
R Seat belts can only work when used
properly. Never wear

seat belts in any other
way than as described in this section, as
that could result in serious injuries in the
event of an accident.
R Each occupant should wear their seat belt
at all times, because seat belts help reduce
the likelihood of and potential severity of
injuries in accidents, including rollovers.
The integrated restraint system includes
SRS (driver front air bag, driver's side knee
bag, front-passenger front air bag, side
impact air bags, window curtain air bags for
the side windows), Emergency Tensioning
Devices, seat belt force limiters, and front
seat knee bolsters.
The system is designed to enhance the
protection offered to properly belted
occupants in certain frontal (front air bags,
driver's side knee bag and ETDs) and side
(side impact air bags, window curtain air
bags, and ETDs) impacts which exceed
preset deployment thresholds and in
certain rollovers (window curtain air bags
and ETDs).
R Never wear the shoulder belt under your
arm, across your neck or off your shoulder.
In a frontal crash, your body would move
too far forward. That would increase the
chance of head and neck injuries. The seat
belt would also apply too much force to the
ribs or abdomen, which could severely
injure internal organs such as your liver or
spleen.
Adjust the seat belt so that the shoulder
section is located as close as possible to
the middle of the shoulder. It should not46
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touch the neck. Never pass the shoulder
portion of
the
seat belt under your arm. For
this purpose, you can adjust the height of
the seat belt outlet.
R Position the lap belt as low as possible on
your hips and not across the abdomen. If
the lap belt is positioned across your
abdomen, it could cause serious injuries in
a crash.
R Never wear seat belts over rigid or
breakable objects in or on your clothing,
such as eyeglasses, pens, keys etc., as
these might cause injuries.
R Make sure the seat belt is always fitted
snugly. Take special care of this when
wearing loose clothing.
R Never use a seat belt for more than one
person at a time. Do not fasten a seat belt
around a person and another person or
other objects at the same time.
R Seat belts should not be worn twisted. In a
crash, you would not have the full width of
the seat belt to distribute impact forces.
The twisted seat belt against your body
could cause injuries.
R Pregnant women should also always use a
lap-shoulder belt. The lap belt portion
should be positioned as low as possible on
the hips to avoid any possible pressure on
the abdomen.
R Place the seat backrest in a position that is
as upright as possible.
R Check your seat belt during travel to make
sure it is properly positioned.
R Never place your feet on the instrument
panel, dashboard, or on the seat. Always
keep both feet on the floor in front of the
seat.
R When using a seat belt to secure infant
restraints, toddler restraints, or children in
booster seats, always follow the child seat
manufacturer's instructions. G
WARNING
Do not pass seat belts over sharp edges. They
could tear.
Do not allow

the seat belt to get caught in the
door or in the seat adjustment mechanism.
This could damage the seat belt.
Never attempt to make modifications to seat
belts. This could impair the effectiveness of
the seat belts.
Fastening seat belts G
WARNING
According to accident statistics, children are
safer when properly restrained on the rear
seats than on

the front-passenger seat. Thus,
we strongly recommend that children be
placed in the rear seat whenever possible.
Regardless of seating position, children 12
years old and under must be seated and
properly secured in an appropriately sized
child restraint system or booster seat
recommended for the size and weight of the
child. For additional information, see the
"Children in the vehicle" section.
A child's risk of serious or fatal injuries is
significantly increased if the child restraints
are not properly secured in the vehicle and/
or the child is not properly secured in the child
restraint. Occupant safety
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X
Adjust the seat and move the backrest to
an almost vertical position ( Y page 86).
X Pull the seat belt smoothly through belt
sash guide :.
X Without twisting it, guide the shoulder
section of the seat belt across the middle
of your shoulder
and the lap section across
your pelvis.
X Engage belt tongue ; in buckle =.
X If necessary, adjust the seat belt to the
appropriate height ( Y page 48).
X If necessary, pull upwards on the shoulder
section of the seat belt to tighten the belt
across your body.
Information on releasing the seat belt with
release button

?(Y page 48).
Belt height adjustment You can adjust the seat belt height on the
front seats. Adjust the belt to a height that
allows the upper part of the seat belt to be
routed across the center of your shoulder.
X
To raise: slide the belt sash guide upwards.
The belt sash guide engages in various
positions.
X To lower: press and hold belt sash guide
release :

.
X Slide the belt sash guide downwards.
X Release belt sash guide release : and
make sure that the belt sash guide has
engaged. Using the seat belt for the center rear-
compartment seat If the left-hand rear seat backrest is folded
down and
back

up again, the rear center seat
belt may lock. The seat belt can then not be
pulled out.
X To release the rear center seat belt: pull
the seat belt out approximately 1 in
(25 mm) at the belt outlet on the backrest
and then release it again.
The seat belt is retracted and released.
Releasing seat belts !
Make sure
that

the seat belt is fully rolled
up. Otherwise, the seat belt or belt tongue
will be trapped in the door or in the seat
mechanism. This could damage the door,
the door trim panel and the seat belt.
Damaged seat belts can no longer fulfill
their protective function and must be
replaced. Visit a qualified specialist
workshop. X
Press release button ?
on belt

buckle =.
X Guide belt tongue ; back to belt sash
guide :.48
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