MERCEDES-BENZ A CLASS 2012 Service Manual

Useful information ..............................
40
Occupant safety .................................. 40
Children in the vehicle ........................50
Driving safety systems ....................... 61
Anti-theft systems .............................. 69 39Safety

Useful information
i This Owner's Manual describes all mod-
els,
series and optional equipment for your
vehicle that were available at the time of
going to press. National variations are pos-
sible. Note that your vehicle may not be
equipped with all of the functions descri-
bed. This is also the case for systems and
functions relevant to safety.
i Read the information on qualified special-
ist workshops: (Y page 24). Occupant safety
Important safety notes
G
WARNING
If service work is not carried out correctly, the
operating
safety of your vehicle may be affec-
ted. This could cause you to lose control of
your vehicle and cause an accident. More-
over, the safety systems may no longer be
able to protect you or others as they are
designed to do.
Always have service work carried out at a
qualified specialist workshop. G
WARNING
Modifications to or work performed incor-
rectly on the following parts can result in the
restraint

systems not functioning as intended:
R the restraint system, consisting of seat
belts and their anchorage points, belt ten-
sioners, belt force limiters and airbags
R the wiring
R networked electronic systems
Airbags and belt tensioners could fail to
deploy or be triggered in an accident despite
the deceleration force being sufficient to trig-
ger the systems, or could be triggered unin-
tentionally. For this reason, never make any
modifications to the restraint systems.
Therefore, you must not tamper with elec-
tronic components or their software. The seat belts, together with SRS (Supple-
mental Restraint System), are complemen-
tary, co-ordinated restraint systems
(Y page 41). They reduce the risk of injury
in specific, pre-defined types of accident sit-
uations and thereby increase occupant
safety. However, seat belts and airbags gen-
erally do not protect against objects pene-
trating the vehicle from the outside.
To ensure that the restraint systems can
deliver their full potential protection, make
sure that:
R
the seat and head restraint are adjusted
properly

(Y page 92)
R the seat belt has been fastened properly
(Y page 46)
R the airbags can inflate unrestricted if
deployed ( Y page 42)
R the steering wheel is adjusted properly
(Y page 98)
R the restraint systems have not been modi-
fied
An airbag increases the protection of vehicle
occupants wearing a seat belt. However, air-
bags are only an additional restraint system
which complements, but does not replace,
the seat belt. All vehicle occupants must wear
their seat belt correctly at all times, even if
the vehicle is equipped with airbags. The air-
bags are not deployed in all types of acci-
dents. For example, if the protective capacity
of correctly fastened seat belts is not
increased by deploying the airbags, the air-
bags will not deploy.
Airbag deployment only provides increased
protection if the seat belt is worn correctly.
The seat belt helps, firstly, to keep the vehicle
occupant in the best position in relation to the
airbag. Secondly, in a head-on collision, for
example, the seat belt prevents the vehicle
occupant from being propelled towards the
point of impact. 40
Occupant safety
Safety

SRS (Supplemental Restraint System)
Introduction Supplemental Restraint System (SRS) with:
R
The 6 SRS warning lamp
R Airbags
R Airbag control unit (with crash sensors)
R Belt
tensioners 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 forces to which occupants are subjected
during an accident.
SRS warning lamp G
WARNING
If SRS is malfunctioning, individual systems
may
be triggered unintentionally or might not
be triggered in the event of an accident with
a high rate of vehicle deceleration.
A malfunction has occurred if:
R the 6 SRS warning lamp does not light
up when the ignition is switched on.
R the engine is running and the 6 SRS
warning lamp does not go out after a few
seconds.
R the engine is running and the 6 SRS
warning lamp lights up again.
In this case, have SRS checked immediately
at a qualified specialist workshop.
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 run-
ning. Therefore, malfunctions can be detec-
ted in good time. Triggering of belt tensioners and air-
bags During the first stage of a collision, the airbag
control unit evaluates important physical
data

relating to vehicle deceleration or accel-
eration, such as:
R duration
R direction
R magnitude
Based on the evaluation of this data, the air-
bag control unit pre-emptively triggers the
belt tensioners in the first stage.
If there is an even higher rate of vehicle decel-
eration or acceleration in a longitudinal direc-
tion, the front airbags are also deployed.
Your vehicle has adaptive, two-stage front air-
bags. The airbag control unit evaluates vehi-
cle deceleration or acceleration in the event
of a collision. In the first deployment stage,
the front airbag is filled with enough propel-
lant gas to reduce the risk of injuries. The
front airbag is fully deployed if a second
deployment threshold is reached within a few
milliseconds.
The belt tensioner and airbag 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 accelera-
tion and the direction of the force are essen-
tially determined by:
R the distribution of forces during the colli-
sion
R the collision angle
R the deformation characteristics of the vehi-
cle
R the characteristics of the object with which
the vehicle has collided
Factors which can only be seen and measured
after a collision has occurred do not play a
decisive role in the deployment of an airbag, Occupant safety
41
Safety Z

nor do they provide an indication of airbag
deployment.
The vehicle may be deformed significantly,
e.g.
the bonnet or the wing, without an airbag
being deployed. This is the case if only parts
which are relatively easily deformed are affec-
ted and the rate of deceleration is not high.
Conversely, airbags may be deployed even
though the vehicle suffers only minor defor-
mation. 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 belt tensioners can only be trig-
gered if the seat belt tongues on the front
seats are correctly engaged in the seat belt
buckles.
i Not all airbags are deployed in an acci-
dent. The different airbag systems work
independently of each other.
How the airbag system works is deter-
mined by predicting the severity of the acci-
dent, especially vehicle deceleration or
acceleration, and the type of accident:
R head-on collision
R side impact
R overturn Airbags
Important safety notes G
WARNING
Airbags provide additional protection; they
are not, however, a substitute for seat belts.
Observe

the following notes to reduce the risk
of serious or even fatal injury caused by airbag
deployment:
R all vehicle occupants – in particular, preg-
nant women – must wear their seat belt
correctly at all times and lean back against
the backrest, which should be positioned
as close to the vertical as possible. The head restraint must support the back of the
head at about eye level.
R always secure children less than
1.50

m tall or under 12 years of age in suit-
able child restraint systems.
R all vehicle occupants must select a seat
position that is as far away from the airbag
as possible. The driver's seat position must
allow the vehicle to be driven safely. The
driver's chest should be as far away from
the centre of the driver's airbag cover as
possible.
R move the front-passenger seat as far back
as possible. This is especially important if
you have secured a child in a child restraint
system on the front-passenger seat.
R vehicle occupants – in particular, children
– must not lean their head into the area of
the window in which the sidebag/window-
bag is deployed.
R rearward-facing child restraint systems
must not be fitted to the front-passenger
seat unless the front-passenger airbag has
been disabled. On the front-passenger
seat, the front-passenger airbag is disabled
if a child restraint system with a trans-
ponder for automatic child seat recognition
is fitted to the front-passenger seat in a
vehicle equipped with automatic child seat
recognition. The 4 PASSENGER AIRBAG
OFF indicator lamp must be continuously
lit.
If the front-passenger seat of your vehicle
does not have automatic child seat recog-
nition, or your rearward-facing child
restraint system does not have a trans-
ponder for automatic child seat recogni-
tion, children must be secured in a child
restraint system on a suitable seat in the
rear. If you secure a forward-facing child
restraint system to the front-passenger
seat, you must move the front-passenger
seat as far back as possible.
R make sure there are no heavy or sharp-
edged objects in the pockets of clothing.42
Occupant safety
Safety

R
do not lean forwards, e.g. over the cover of
the driver's/front-passenger front airbag,
particularly when the vehicle is in motion.
R do not put your feet on the dashboard.
R only hold the steering wheel on the outside.
This allows the airbag to be fully deployed.
You could be injured if the airbag is
deployed and you are holding the inside of
the steering wheel.
R do not lean on the doors from inside the
vehicle.
R make sure that there are no people, ani-
mals or objects between the vehicle occu-
pants and the area where the airbags are
deployed.
R do not place any objects between the seat
backrest and the door.
R do not hang any hard objects, e.g. coat
hangers, on the grab handles or coat hooks.
R do not attach accessories, e.g. cup holders,
to the doors.
It is not possible to rule out a risk of injury
being caused by an airbag, due to the high
speed at which the airbag must be deployed. G
WARNING
Airbag functionality can only be assured if the
following
parts are not covered and no badges
or stickers are attached to them:
R padded steering wheel boss
R kneebag cover below the steering column
R front-passenger airbag cover
R outer side of front seat bolsters
R side trim next to the rear seat backrest
R roof frame cover between the front A-pillar
and the C-pillar in the rear compartment G
WARNING
When an airbag deploys, a small amount of
powder is released. The powder may cause
short-term breathing difficulties to persons
suffering from asthma or other pulmonary
conditions. In order to prevent potential breathing diffi-
culties, you should leave the vehicle as soon
as it is safe to do so. You can also open the
window

to allow fresh air to enter the vehicle
interior. The powder does not constitute a
health hazard and does not indicate that there
is a fire in the vehicle. G
WARNING
The airbag parts are hot after the airbag has
been deployed. Do not touch them as you
could burn yourself.
Have the airbags replaced at a qualified spe-
cialist workshop. Otherwise, occupants are
not protected by the airbags in the event of
another accident.
Airbag deployment slows down and restricts
the movement of the vehicle occupant.
If the airbags 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 airbag installation locations are identified
by the AIRBAG symbol.
Front airbags !
Do not place heavy objects on the front-
passenger seat. The system may then
detect

that the seat is occupied and if there
is an accident, the restraint systems on the
front-passenger side could be deployed.
Have restraint systems that have been trig-
gered replaced. Occupant safety
43
Safety Z

Driver's airbag
: deploys in front of the
steering wheel; front-passenger front air-
bag ;
deploys in front of and above the glove
compartment.
The front airbags 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 if the system determines that airbag
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 airbags in the vehi-
cle
If the vehicle overturns, the front airbags are
generally not deployed.
Vehicles with automatic child seat recog-
nition in the front-passenger seat: front-
passenger airbag ; is only activated if the
system determines that the front-passenger
seat is occupied. The 4 PASSENGER AIR-
BAG OFF indicator lamp on the centre con-
sole does not light up (Y page 52). If a child restraint system is fitted to the front-
passenger

seat and the PASSENGER AIRBAG
OFF 4 indicator lamp on the centre con-
sole is not on:
R a child restraint system without a trans-
ponder for automatic child seat recognition
has been fitted or
R a child restraint system with a transponder
has been fitted incorrectly
Driver's kneebag Driver's kneebag
:
deploys under the steer-
ing column. The driver's kneebag is triggered
together with the front airbag. The driver's
kneebag is designed to operate together with
the front airbag in frontal impacts if certain
thresholds are exceeded. The driver's knee-
bag operates best in conjunction with cor-
rectly positioned and fastened seat belts.
Driver's kneebag : increases the driver's
protection against:
R knee injuries
R thigh injuries
R lower leg injuries
Sidebags G
WARNING
If you wish to use seat covers, Mercedes-Benz
recommends that, for safety reasons, you
only

use seat covers that have been approved
for Mercedes-Benz vehicles.
The seat covers must have a special tear seam
for sidebags. Otherwise, the sidebags cannot 44
Occupant safety
Safety

deploy correctly and would fail to provide the
intended protection in the event of an acci-
dent. Appropriate seat covers can be
obtained,
for example, from a Mercedes-Benz
Service Centre. Front sidebags : and rear sidebags
;
deploy next to the outer seat cushions.
When

deployed, the sidebags 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 sidebags 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 accelera-
tion, e.g. in a side impact
R independently of the use of the seat belt
R independently of the front airbags
R independently of the belt tensioners
If the vehicle overturns, the sidebags are gen-
erally not deployed. Sidebags are deployed if
the system detects high vehicle deceleration
or acceleration in a lateral direction and
determines that sidebag deployment can
offer additional protection to that provided by
the seat belt. Windowbags
Windowbags
: enhance the level of protec-
tion for the head (but not chest or arms), of
the

vehicle occupants on the side of the vehi-
cle on which the impact occurs.
Windowbags : are integrated into the side
of the roof frame and deployed in the area
from the A-pillar to the C-pillar.
Windowbags are deployed:
R at the start of an accident with a high rate
of lateral vehicle deceleration or accelera-
tion, e.g. in a side impact
R on the side on which an impact occurs
R on the driver's and the front passenger's
side if the vehicle overturns and the system
determines that deployment can offer addi-
tional 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 airbags PRE-SAFE
®
(anticipatory occupant
protection) G
WARNING
When adjusting the seat, make sure that
nobody can become trapped.
! Make

sure that there are no objects in the
footwell or behind the seats when moving
the seat back. There is a risk that the seats
and/or the objects could be damaged. Occupant safety
45
Safety Z

PRE-SAFE
®
takes pre-emptive measures to
protect occupants in certain hazardous sit-
uations.
PRE-SAFE ®
intervenes:
R when BAS activates, e.g. in emergency
braking situations
R when adaptive Brake Assist intervenes
powerfully on vehicles with DISTRONIC
PLUS
R in
critical driving situations, e.g. when phys-
ical limits are exceeded and the vehicle
understeers or oversteers severely
PRE-SAFE ®
takes the following measures
depending on the hazardous situation detec-
ted:
R the front seat belts are pre-tensioned.
R vehicles with the memory function: the
front-passenger seat is adjusted if it is in an
unfavourable position.
R if the vehicle skids, the panorama sliding
sunroof and the side windows are closed so
that only a small gap remains.
If the hazardous situation passes without
resulting in an accident, PRE-SAFE ®
slackens
the belt pretensioning. All settings made by
PRE-SAFE ®
can then be reversed.
If the seat belts are not released:
X Move the backrest or seat back slightly, but
only when the vehicle is stationary.
The belt pretensioning is reduced and the
locking mechanism is released.
More information about seat belt adjustment,
a convenience function integrated into PRE-
SAFE

(Y page 47). Seat belts
Important safety notes G
WARNING
A seat belt which is not worn correctly, or
which has not been engaged in the seat belt
buckle

correctly, cannot provide the intended
level of protection. Under certain circumstan- ces, this could cause severe or even fatal inju-
ries in the event of an accident.
Therefore, make sure that all occupants — in
particular,

pregnant women — wear their seat
belts correctly at all times.
R The seat belt must fit snugly on your body
and must not be twisted.Therefore, avoid
wearing bulky clothing, e.g. a winter coat.
The shoulder section of the belt must be
routed across the centre of your shoulder
— on no account across your neck or under
your arm — and pulled tight against your
upper body. The lap belt must always pass
across your lap as low down as possible, i.e.
over your hip joints — not across your abdo-
men. If necessary, push the seat belt
slightly downwards and adjust it by pulling
it in the direction the seat belt retracts.
R Do not route the seat belt strap over sharp
or fragile objects. Please make sure that
such objects are not on or in your clothing,
e.g. spectacles, pens or keys etc. The seat
belt strap could become damaged and tear
during an accident and you or other vehicle
occupants could be injured.
R Only one person should use each seat belt
at any one time. Children must never travel
sitting on the lap of another occupant. The
child will not be secured in the event of an
accident, heavy braking or sudden change
of direction. This may result in the child or
other occupants being seriously or fatally
injured.
R Persons under 1.50 m tall cannot wear the
seat belts correctly. For this reason secure
persons less than 1.50 m tall in specially
designed, suitable restraint systems.
R Children under 1.50 m tall and younger
than twelve years of age cannot wear the
seat belts correctly. For this reason secure
them in special suitable child restraint sys-
tems installed on a suitable seat. Additional
information can be found in the Operating
Instructions in the chapter "Safety", "Chil-
dren in the Vehicle". Observe the installa-46
Occupant safety
Safety

tion instructions of the child restraint sys-
tem manufacturer.
R Do not secure an object with a seat belt if
the seat belt is also being used by one of
the vehicle's occupants. G
WARNING
The seat belt does not offer the intended level
of protection unless the backrest is almost
vertical. Under certain circumstances, this
could
cause severe or even fatal injuries in the
event of an accident.
Before starting a journey, make sure that the
seat is properly adjusted and that the back-
rest is almost vertical. G
WARNING
A dirty or damaged seat belt or one that has
been modified or subjected to a load in an
accident

no longer offers the intended level of
protection. Under certain circumstances, this
could cause severe or even fatal injuries in the
event of an accident.
For this reason, check regularly that the seat
belts are not damaged or dirty.
Always have damaged seat belts or seat belts
that have been subjected to a load in an acci-
dent replaced at a qualified specialist work-
shop.
For safety reasons, Mercedes-Benz recom-
mends that you only use seat belts which have
been approved by Mercedes-Benz for your
vehicle.
Seat belts are the most effective means of
restraining the movement of vehicle occu-
pants in the event of an accident. This
reduces the risk of vehicle occupants coming
into contact with parts of the vehicle interior. Fastening seat belts
X
Adjust the seat and move the backrest to
an almost vertical position ( Y page 92).
X Pull the seat belt smoothly through belt
sash guide :.
X Without twisting it, guide the shoulder sec-
tion of the seat belt across the middle of
your shoulder and the lap section across
your pelvis.
X Engage belt tongue ; in buckle =.
Seat
belt adjustment: if necessary, the driv-
er's and front-passenger seat belts auto-
matically adjust to the upper body
(Y page 47).
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).
Seat belt adjustment The seat-belt adjustment function adjusts the
driver's and front-passenger seat belt to the
upper body of the occupants. Occupant safety
47
Safety Z

The belt strap is tightened slightly when:
R
you engage the belt tongue in the belt
buckle
and you then turn the key to position
2 in the ignition lock.
R the key is in position 2 in the ignition lock
and you then engage the belt tongue in the
buckle.
The seat-belt adjustment will apply a certain
tightening force if any slack is detected
between the occupant and the seat belt. Do
not hold on to the seat belt tightly while it is
adjusting. You can switch the seat-belt
adjustment on and off in the on-board com-
puter ( Y page 225).
The seat-belt adjustment is an integral part of
the PRE-SAFE ®
convenience function. More
information about PRE-SAFE ®
can be found
in the "PRE-SAFE ®
(preventative occupant
protection)" section (Y page 45).
Belt height adjustment You can adjust the belt height for the front
seats. Adjust the belt to a height that allows
the upper part of the seat belt to be routed
across the centre of your shoulder.
X
To raise:
slide the belt sash guide upwards.
The belt sash guide engages in various posi-
tions.
X To lower: press and hold belt sash guide
release :.
X Slide the belt sash guide downwards.
X Let go of belt sash guide release : and
make sure that the belt sash guide has
engaged. Releasing the 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. Dam-
aged seat belts can no longer fulfil 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 :.
Belt warning for the driver and front
passenger The
7
seat belt warning lamp in the instru-
ment cluster is a reminder for all occupants
to fasten their seat belts. It may light up con-
tinuously or flash. In addition, a warning tone
may sound.
The 7 seat belt warning lamp goes out and
the warning tone ceases when the driver and
the front passenger have fastened their seat
belt.
For certain countries only: regardless of
whether the driver and the front passenger
have fastened their seat belts, the 7 seat
belt warning lamp lights up for six seconds
after the engine is started. It then goes out if 48
Occupant safety
Safety