2012 MERCEDES-BENZ A CLASS sensor

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

Warning notice on the front-passenger sun visor
Warning symbol for a rearward-facing child
restraint system
Do not use a rearward-facing child restraint
system on a seat that is protected by an air-
bag installed in front of it.
Automatic
child seat recognition on the
front-passenger seat G
WARNING
If the 4 PASSENGER AIRBAG OFF indica-
tor lamp does not light up when the child
restraint

system is fitted, the front-passenger
airbag has not been disabled. If the front-
passenger airbag deploys, the child could be
seriously or even fatally injured.
Proceed as follows:
R do not use a rearward-facing child restraint
system on the front-passenger seat.
R fit a rearward-facing child restraint system
on a suitable rear seat.
or R
only use a forward-facing child restraint
system on the front-passenger seat and
move the front-passenger seat to the rear-
most position.
R have the automatic child seat recognition
checked

at a qualified specialist workshop.
To ensure that the automatic child seat rec-
ognition on the front-passenger seat func-
tions/communicates correctly, never place
objects, e.g. a cushion, under the child
restraint system. The entire base of the child
restraint system must always rest on the seat
cushion. An incorrectly fitted child restraint
system cannot perform its intended protec-
tive function in the event of an accident, and
could lead to injuries. G
WARNING
Do not place electronic devices on the front-
passenger seat, e.g.:
R laptops, when switched on
R mobile phones
R cards

with transponders, e.g. ski passes or
access cards
Signals from electronic equipment can cause
interference in the automatic child seat rec-
ognition sensor system. This can lead to a
system malfunction. This may cause the
4 PASSENGER AIRBAG OFF indicator
lamp to light up without there being a child
seat with transponders for automatic child
seat recognition fitted. The front-passenger
airbag will not then deploy during an accident.
It is also possible that the 6 SRS warning
lamp lights up and/or the 4 PASSENGER
AIRBAG OFF indicator lamp does not light up
briefly when you turn the key in the ignition
lock to position 2.52
Children in the vehicle
Safety

If the front-passenger seat of your vehicle
does not have automatic child seat recogni-
tion,
this is indicated by a special sticker. The
sticker is affixed to the side of the dashboard
on the front-passenger side. The sticker is
visible when you open the front-passenger
door.
Vehicles without automatic child seat recog-
nition on the front-passenger seat: if you turn
the key to position 2 in the ignition lock, the
45 indicator lamp lights up briefly but
has no function. It does not indicate that there
is automatic child seat recognition on the
front-passenger seat. The sensor system for child restraint systems
in the front-passenger seat detects whether
a special Mercedes-Benz child seat with a
transponder for automatic child seat recog-
nition has been fitted. In this case,
45 indicator lamp
: lights up. The
front-passenger front airbag is disabled. i
If the front-passenger front airbag is dis-
abled by the automatic child seat recogni-
tion, the following remain enabled on the
front-passenger side:
R the sidebag
R the windowbag
R the belt tensioner
ISOFIX child seat securing system for
the rear seats G
WARNING
A child restraint system secured by the ISOFIX
child seat securing system does not provide
sufficient protection for children weighing
more than 22 kg

. For this reason, do not
secure children weighing more than 22 kg in
a child restraint system secured by the ISOFIX
child seat securing system. If the child weighs
more than 22 kg, secure the child restraint
system with the vehicle seat belt as well. In
addition, when fitting a child restraint system,
be sure to observe the manufacturer's instal-
lation instructions and the instructions for
correct use of the child restraint system. G
WARNING
The child restraint system cannot perform its
protective function if it is not correctly fitted
to

a suitable vehicle seat. The child cannot be
restrained in the event of an accident, heavy
braking or sudden changes of direction. The
child could be seriously or even fatally injured.
For this reason, when fitting a child restraint
system, be sure to observe the manufactur-
er's installation instructions and the instruc-
tions for correct use of the child restraint sys-
tem.
For safety reasons, when installing child
restraint systems on the rear seats, only use
child restraint systems with the ISOFIX child
seat securing system, which are specially tes-
ted and approved for Mercedes-Benz vehi-
cles.
An incorrectly fitted child restraint system
could come loose and seriously or even fatally Children in the vehicle
53
Safety
Z

G
WARNING
The distance warning function cannot always
clearly identify objects and complex traffic
situations.
In such cases, the distance warning function
may:
R give an unnecessary warning
R not give a warning
There is a risk of an accident.
Always
pay careful attention to the traffic sit-
uation; do not rely on the distance warning
function alone.
Function
X To activate/deactivate:
activate or deac-
tivate the distance warning function in the
on-board computer (Y page 218).
Vehicles with a black and white multi-
function
display: when the distance warning
function is activated, the Ä symbol
appears in the status overview in the multi-
function display.
Vehicles with a colour multifunction dis-
play: when the distance warning function is
deactivated, the æ symbol appears in the
assistance graphics in the multifunction dis-
play.
The distance warning function can help you
to minimise the risk of a front-end collision
with a vehicle ahead or reduce the effects of
such a collision. If the distance warning func-
tion detects that there is a risk of a collision,
you will be warned visually and acoustically.
Without your intervention, the distance warn-
ing function cannot prevent a collision.
The distance warning function issues a warn-
ing at speeds:
R of around 30 km/h or more, if, over several
seconds, the distance maintained to the
vehicle travelling in front is insufficient. The
· distance warning lamp then lights up
in the instrument cluster.
R of around 7 km/h or higher, if you very
quickly approach a vehicle in front. An
intermittent warning tone will then sound, and the · distance warning lamp will
light up in the instrument cluster.
X Brake immediately in order to increase the
distance from the vehicle in front.
or
X Take evasive action provided it is safe to do
so.
Due to the nature of the system, particularly
complicated but non-critical driving condi-
tions

may also cause the system to display a
warning.
With the help of the radar sensor system, the
distance warning function can detect obsta-
cles that are in the path of your vehicle for an
extended period of time.
Up to a speed of around 70 km/h, the dis-
tance warning function can also react to sta-
tionary obstacles, such as stopped or parked
vehicles.
If you approach an obstacle and the distance
warning function detects a risk of a collision,
the system will alert you both visually and
acoustically.
In particular, the detection of obstacles can
be impaired in the case of:
R dirt on the sensors or obscured sensors
R snow or heavy rain
R interference by other radar sources
R strong radar reflections, for example, in
multi-storey car parks
R a narrow vehicle travelling in front, e.g. a
motorcycle
R a vehicle travelling in front on a different
line
Following damage to the front end of the vehi-
cle, have the configuration and operation of
the radar sensor checked at a qualified spe-
cialist workshop. This also applies to colli-
sions at slow speeds where there is no visible
damage to the front of the vehicle. Driving safety systems
63Safety Z

Adaptive Brake Assist
i
Observe the "Important safety notes" sec-
tion for driving safety systems
(Y page 61). G
WARNING
Adaptive Brake Assist cannot always clearly
identify objects and complex traffic situa-
tions. In these cases, Adaptive Brake Assist
may not intervene. There is a risk of an acci-
dent.
Always

pay careful attention to the traffic sit-
uation and be ready to brake. G
WARNING
Adaptive Brake Assist does not react:
R to people or animals
R to oncoming vehicles
R to crossing traffic
R to stationary obstacles
R when cornering
As a result, Adaptive Brake Assist may not
intervene in all critical conditions. There is a
risk of an accident.
Always

pay careful attention to the traffic sit-
uation and be ready to brake.
Adaptive Brake Assist aids you in braking dur-
ing hazardous situations at speeds above
30 km/h and uses the radar sensor system
to evaluate the traffic situation.
With the help of a sensor system, adaptive
Brake Assist can detect obstacles that are in
the path of your vehicle for an extended
period of time.
Should you approach an obstacle and adap-
tive Brake Assist has detected a risk of colli-
sion, adaptive Brake Assist calculates the
braking force necessary to avoid a collision.
Should you apply the brakes forcefully, adap-
tive Brake Assist will automatically increase
the braking force to a level suitable for the
traffic conditions. X
Keep the brake pedal depressed until the
emergency braking situation is over.
ABS prevents the wheels from locking.
The brakes will work normally again if:
R you release the brake pedal
R there

is no longer any danger of a collision
R no obstacle is detected in front of your
vehicle
Adaptive Brake Assist is then deactivated.
Vehicles with PRE-SAFE ®
: if adaptive Brake
Assist requires particularly high brake pres-
sure, preventative passenger protection
measures (PRE-SAFE ®
) are deployed simul-
taneously.
Up to vehicle speeds of around 250 km/h,
adaptive Brake Assist is capable of reacting
to moving objects that have already been rec-
ognised as such at least once over the period
of observation. Adaptive Brake Assist does
not react to stationary obstacles.
If adaptive Brake Assist is not available due
to a malfunction in the radar sensor system,
the brake system remains available with full
brake boosting effect and BAS.
In particular, the detection of obstacles can
be impaired if there is:
R dirt on the sensors or anything else cover-
ing the sensors
R snow or heavy rain
R interference by other radar sources
R the possibility of strong radar reflections,
for example, in multi-storey car parks
R a narrow vehicle travelling in front, e.g. a
motorcycle
R a vehicle travelling in front on a different
line
Following damage to the front end of the vehi-
cle, have the configuration and operation of
the radar sensor checked at a qualified spe-
cialist workshop. This also applies to colli-
sions at slow speeds where there is no visible
damage to the front of the vehicle. 64
Driving safety systems
Safety

A visual and audible alarm is triggered if the
alarm system is primed and you open:
R
the vehicle with the emergency key ele-
ment
R a door
R the tailgate
R the bonnet
X To stop the alarm: insert the key into the
ignition lock.
The alarm is switched off.
or
X Press the % or & button on the key.
The alarm is switched off.
The alarm is not switched off, even if you
close the open door that has triggered it, for
example. Tow-away protection
Function An audible and visual alarm is triggered if your
vehicle's angle of inclination is altered while
tow-away

protection is primed. This can occur
if the vehicle is jacked up on one side, for
example.
Activating X
Make sure that:
R
the doors are closed.
R the tailgate is closed.
Only then is the tow-away protection
primed.
X Lock the vehicle with the key.
Tow-away protection is primed after
approximately

60 seconds.
Deactivating X
Unlock the vehicle with the key.
or
X Insert the key into the ignition lock.
Tow-away protection is switched off auto-
matically. Deactivating
X
Remove the key from the ignition lock.
X Press button :.
Indicator lamp ; lights up briefly.
X Lock the vehicle with the key.
Tow-away protection is deactivated.
Tow-away protection remains deactivated
until:
R the vehicle is unlocked again
R a door is opened and closed again
R the vehicle is locked again
To prevent a false alarm, deactivate the tow-
away protection if you lock your vehicle and
it:
R is being transported
R is being loaded onto a ferry or car trans-
porter, for example
R is parked on a movable surface, e.g. in a
split-level garage Interior motion sensor
Function When the interior motion sensor is primed, a
visual

and audible alarm is triggered if move-
ment is detected in the vehicle interior. This
can occur if someone reaches into the vehicle
interior, for example. 70
Anti-theft systems
Safety

Activating
X
Make sure that:
R
the side windows are closed.
R the panorama sliding sunroof is closed.
R there
are no objects, e.g. mascots, hang-
ing on the rear-view mirror or on the grab
handles on the roof trim.
This will prevent false alarms.
X Make sure that:
R
the doors are closed.
R the panorama sliding sunroof is closed.
R the tailgate is closed.
Only then is the interior motion sensor
primed.
X Lock the vehicle with the key.
The interior motion sensor is primed after
approximately

30 seconds.
Deactivating X
Unlock the vehicle with the key.
or
X Insert the key into the ignition lock.
The interior motion sensor is switched off
automatically.
Deactivating X
Remove the key from the ignition lock.
X Press button :.
Indicator lamp ; flashes briefly.
X Lock the vehicle with the key.
The interior motion sensor is deactivated. The interior motion sensor remains deactiva-
ted until:
R
the vehicle is unlocked again
R a door is opened and closed again
R the vehicle is locked again
To prevent a false alarm, deactivate the inte-
rior motion sensor if you lock your vehicle
and:
R people or animals remain in the vehicle.
R the panorama sliding sunroof remains
open.
R the side windows remain open.
i UK only: your vehicle is equipped with a
double lock function. The doors cannot be
opened from the inside if the vehicle has
been locked with the key ( Y page 80).
Deactivate the interior motion sensor
before you lock the vehicle with the key.
The doors can then be opened from the
inside after the vehicle has been locked
from

the outside with the key. Observe the
"Important safety notes" (Y page 79). Anti-theft systems
71
Safety Z

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). Key
Important safety notes
G
WARNING
If children are left unsupervised in the vehicle,
they could:
R open the doors, thus endangering other
people or road users.
R get out and disrupt traffic.
R operate the vehicle's equipment.
Additionally, children could set the vehicle in
motion if, for example, they:
R release the parking brake.
R shift the automatic transmission out of
parking position P.
R shift the manual transmission into neutral.
R start the engine.
There is a risk of an accident and injury.
When

leaving the vehicle, always take the key
with you and lock the vehicle. Never leave
children or animals unattended in the vehicle.
Always keep the key out of reach of children. G
WARNING
If persons (particularly children) are exposed
to heat or cold for a prolonged period, there
is

a risk of serious or even fatal injuries. Never
leave persons (particularly children) unatten-
ded in the vehicle. G
WARNING
If you attach heavy or large objects to the key,
the
key could be unintentionally turned in the
ignition lock. This could cause the engine to
be switched off. There is a risk of an accident.
Do not attach any heavy or large objects to
the key. Remove any bulky keyrings before
inserting the key into the ignition lock.
! Keep the key away from strong magnetic
fields. Otherwise, the remote control func-
tion could be affected.
Strong magnetic fields can occur in the
vicinity of powerful electrical installations.
Do not keep the key:
R with electronic devices, e.g. a mobile
phone or another key
R with metallic objects, e.g. coins or metal
film
R inside metallic objects, e.g. a metal case
United Kingdom only: G
WARNING
When the double locks are activated, the
doors can no longer be opened from the
inside.

People in the vehicle can no longer get
out, e.g. in hazardous situations. There is a
risk of injury.
Therefore, do not leave any people unsuper-
vised in the vehicle, particularly children, eld-
erly people or people in need of special assis-
tance. Do not activate the double lock when
people are in the vehicle.
If the vehicle has been locked with the key,
then the double lock function is activated as
standard. You can deactivate the double lock
function by deactivating the interior motion
sensor (Y page 70). The doors can then be
opened from the inside after the vehicle has
been locked from the outside. The anti-theft
alarm system is triggered if the door is
opened from the inside. Switch off the alarm
(Y page 69). 74
Key
Opening and closing