warning MERCEDES-BENZ C-Class SEDAN 2012 W204 Service Manual

GWARNING
If the BAS malfunctions, the brake system still
functions, but without the additional brake
boost available that the BAS would normally
provide in an emergency braking maneuver.
Therefore, the braking distance may increase.
BAS PLUS (Brake Assist System Plus)
BAS PLUS is only available in vehicles
equipped with DISTRONIC PLUS.
i Observe the "Important safety notes"
section ( Y page 59).
At speeds above approximately
20 mph (30 km/h), BAS PLUS assists you
when braking in hazardous situations and
uses the radar sensor system to evaluate the
traffic conditions.
i This device has been approved by the FCC
as a "Vehicular Radar System". The radar
sensor is intended for use in an automotive
radar system only. Removal, tampering, or
altering of the device will void any
warranties, and is not permitted by the
FCC. Do not tamper with, alter, or use in
any non-approved way.
Any unauthorized modification to this
device could void the user's authority to
operate the equipment.
With the help of the radar sensor system, BAS
PLUS can detect obstacles that are in the
path of your vehicle for an extended period of
time.
At speeds up to approximately
40 mph (70 km/h), BAS PLUS can also detect
stationary obstacles, for example stopped or
parked vehicles.
Should you approach an obstacle and BAS
PLUS has detected a risk of collision, BAS
PLUS calculates the braking force necessary
to avoid a rear-end collision. Should you apply
the brakes forcefully, BAS PLUS can
automatically increase the braking force to a
level suitable for the traffic conditions.
XKeep 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 rear-end
collision.
R no obstacle is detected in front of your
vehicle.
BAS PLUS is then deactivated.
For BAS PLUS to assist you when driving, the
radar sensor system must be switched on and
operational, see "Radar sensor system" in the
index.
GWARNING
BAS PLUS cannot always clearly identify
objects and complex traffic situations. BAS
PLUS cannot intervene in these cases.
There is a risk of an accident. Always pay
careful attention to the traffic situation and be
ready to brake.
In particular, the detection of obstacles can
be impaired if there is:
R dirt on the sensors or anything else
covering the sensors
R snow or heavy rain
R interference by other radar sources
R the possibility of strong radar reflections,
for example in parking garages
R a narrow vehicle traveling in front, e.g. a
motorbike
R a vehicle traveling in front on a different line
GWARNING
BAS PLUS does not react:
R to people or animals
R to oncoming vehicles
R to crossing traffic
R in curves
As a result, BAS PLUS cannot intervene in
critical situations. There is a risk of an
60Driving safety systemsSafety

accident. Always pay careful attention to the
traffic situation and be ready to brake.
Following damage to the front end of the
vehicle, have the configuration and operation
of the radar sensors checked at a qualified
specialist workshop. This also applies to
collisions at low speeds where there is no
visible damage to the front of the vehicle.
If BAS PLUS is not available due to a
malfunction in the radar sensor system, the
brake system remains available with full
brake boosting effect and BAS.
ESP ®
(Electronic Stability Program)
Important safety notes
i See the "Important safety notes" section
( Y page 59).
If ESP ®
detects that the vehicle is deviating
from the direction desired by the driver, one
or more wheels are braked to stabilize the
vehicle. If necessary, the engine output is also
modified to keep the vehicle on the desired
course within physical limits. ESP ®
assists
the driver when pulling away on wet or
slippery roads. ESP ®
can also stabilize the
vehicle during braking.
If ESP ®
intervenes, the ÷ ESP®
warning
lamp flashes in the instrument cluster.
GWARNING
Under no circumstances should you
deactivate ESP ®
when the ÷ ESP®
warning lamp in the instrument cluster
flashes. Proceed as follows:
R when driving off, apply as little throttle as
possible.
R while driving, ease up on the accelerator
pedal.
R adapt your speed to suit the prevailing road
and weather conditions.
Failure to observe these guidelines could
cause the vehicle to skid. ESP ®
cannot
prevent accidents resulting from excessive
speed.
! Vehicles without 4MATIC: switch the
ignition off when:
R the parking brake is being tested using a
dynamometer
R the vehicle is being towed with the front
axle raised
Application of the brakes by ESP ®
may
otherwise destroy the brake system.
! Vehicles with 4MATIC: switch off the
ignition when the parking brake is being
tested on a brake dynamometer.
Application of the brakes by ESP ®
may
otherwise destroy the brake system.
! Vehicles with 4MATIC: function or
performance tests may only be carried out
on a 2-axle dynamometer. If you wish to
operate the vehicle on such a
dynamometer, please consult an
authorized Mercedes-Benz Center in
advance. You could otherwise damage the
drive train or the brake system.
i Only use wheels with the recommended
tire sizes. Only then will ESP ®
function
properly.
ETS/4ETS (Electronic Traction System)GWARNING
Observe "Important safety notes"
( Y page 58).
Traction control is part of ESP ®
.
Traction control brakes the drive wheels
individually if they spin. This enables you to
pull away and accelerate on slippery surfaces,
for example if the road surface is slippery on
one side. On vehicles with 4MATIC, more
drive torque is also transferred to the wheel
or wheels with traction.
Traction control remains active if you
deactivate ESP ®
.
Driving safety systems61SafetyZ

Deactivating/activating ESP®
(except
AMG vehicles)GWARNING
ESP ®
should not be deactivated during
normal driving other than in the
circumstances described below. Disabling
the system will reduce vehicle stability in
driving maneuvers.
Do not deactivate ESP ®
when the emergency
or spare wheel is mounted.
ESP ®
is activated automatically when the
engine is started.
It may be best to deactivate ESP ®
in the
following situations:
R when using snow chains
R in deep snow
R on sand or gravel
GWARNING
Switch on ESP ®
immediately if one of the
previously stated conditions is no longer met.
Otherwise, ESP ®
cannot stabilize the vehicle
if it begins to lurch or when a wheel spins.
If you deactivate ESP ®
:
R ESP ®
no longer improves driving stability.
R the engine's torque is no longer limited and
the drive wheels can spin. The spinning of
the wheels results in a cutting action, which
provides better grip.
R traction control is still activated.
R ESP ®
still provides support when you
brake.
If ESP ®
is deactivated and one or more wheels
start to spin, the ÷ ESP®
warning lamp in
the instrument cluster flashes. In such
situations, ESP ®
will not stabilize the vehicle.
XTo deactivate: (Y page 204).
The å ESP®
OFF warning lamp in the
instrument cluster lights up.GWARNING
When the å ESP®
OFF warning lamp is lit,
ESP ®
is deactivated.
If the ÷ ESP®
warning lamp and the
å ESP®
OFF warning lamp remain lit,
ESP ®
is not available due to a malfunction.
When ESP ®
is deactivated or not operational,
vehicle stability in standard driving
maneuvers is reduced.
Adapt your speed and driving to the prevailing
road conditions and to the non-operating
status of the ESP ®
.
! Avoid spinning the driven wheels for an
extended period with ESP ®
deactivated.
You could otherwise damage the drivetrain.
XTo activate: (Y page 204).
The å ESP®
OFF warning lamp in the
instrument cluster goes out.
Deactivating/activating ESP ®
(AMG
vehicles)
Activating/deactivating SPORT handling
mode
GWARNING
The SPORT handling mode should not be
switched on during normal driving.
Switching on the SPORT handling mode will
result in the following:
R no restriction to the engine torque
R system supported traction control is
limited
The SPORT handling mode is designed for
driving on closed tracks when the vehicle's
own natural oversteer and understeer
characteristics are desired and requires a
highly skilled and experienced driver able to
handle these critical driving situations.
You could lose control of your vehicle and
cause an accident.
Please be aware of these limits when you
switch on the SPORT handling mode.
62Driving safety systemsSafety

Do not switch on the SPORT handling when a
spare wheel is mounted.
ESP ®
is activated automatically when the
engine is started.
It may be best to activate SPORT handling
mode in the following situations:
R when using snow chains
R in deep snow
R on sand or gravelGWARNING
Switch off the SPORT handling mode and
switch on the ESP ®
immediately if the
aforementioned circumstances do not apply
anymore. Otherwise the SPORT handling
mode will only stabilize the vehicle to a limited
extent when it is starting to skid or a wheel is
spinning.
When SPORT handling mode is activated:
R ESP ®
only improves driving stability to a
limited degree.
R the engine's torque is restricted only to a
limited degree and the drive wheels can
spin. The spinning of the wheels results in
a cutting action, which provides better grip.
R traction control is still activated.
R ESP ®
still provides support when you brake
firmly.
If SPORT handling mode is activated and one
or more wheels start to spin, the ÷ ESP®
warning lamp in the instrument cluster
flashes. ESP ®
only stabilizes the vehicle to a
limited degree.
XTo activate: briefly press button :.
The M SPORT handling mode warning
lamp in the instrument cluster lights up.
The SPORT handling mode message
appears in the multifunction display.XTo deactivate: briefly press button :.
The M SPORT handling mode warning
lamp in the instrument cluster goes out.
Activating/deactivating ESP ®
GWARNING
The ESP
®
should not be switched off during
normal driving.
Disabling of the system will result in the
following:
R no restriction to engine torque
R loss of system-supported traction control
"ESP ®
OFF" is designed for driving on closed
tracks when the vehicle's natural oversteer
and understeer characteristics are desired
and requires a highly skilled and experienced
driver able to handle these critical driving
situations.
You could lose control of your vehicle and
cause an accident.
Please be aware of these limits when you
switch off the ESP ®
.
Do not switch off the ESP ®
when a spare
wheel is mounted.
ESP ®
is activated automatically when the
engine is started.
It may be best to deactivate ESP ®
in the
following situations:
R when using snow chains
R in deep snow
R on sand or gravel
GWARNING
Switch on ESP ®
immediately if one of the
previously stated conditions is no longer met.
Otherwise, ESP ®
cannot stabilize the vehicle
if it begins to lurch or when a wheel spins.
Driving safety systems63SafetyZ

If you deactivate ESP®
:
R ESP ®
no longer improves driving stability.
R the engine's torque is no longer limited and
the drive wheels are able to spin. The
spinning of the wheels results in a cutting
action, which provides better grip.
R traction control is still activated.
R PRE-SAFE ®
Brake is no longer available,
nor is it activated if you brake firmly and
ESP ®
intervenes.
R ESP ®
still provides support when you brake
firmly.
If ESP ®
is deactivated and one or more wheels
start to spin, the ÷ ESP®
warning lamp in
the instrument cluster does not flash. In such
situations, ESP ®
will not stabilize the vehicle.XTo deactivate: press button : until the
å ESP®
OFF warning lamp lights up in
the instrument cluster.
The ÷ OFF message appears in the
multifunction display.GWARNING
When the å ESP®
OFF warning lamp is lit,
ESP ®
is deactivated.
If the ÷ ESP®
warning lamp and the
å ESP®
OFF warning lamp remain lit,
ESP ®
is not available due to a malfunction.
When ESP ®
is deactivated or not operational,
vehicle stability in standard driving
maneuvers is reduced.
Adapt your speed and driving to the prevailing
road conditions and to the non-operating
status of the ESP ®
.
! Avoid spinning the driven wheels for an
extended period with ESP ®
deactivated.
You could otherwise damage the drivetrain.XTo activate: briefly press button :.
The å ESP®
OFF warning lamp in the
instrument cluster goes out. The ÷ON
message appears in the multifunction
display.
EBD (electronic brake force
distribution)
i Observe the "Important safety notes"
section ( Y page 59).
EBD monitors and controls the brake
pressure on the rear wheels to improve
driving stability while braking.
GWARNING
If EBD has malfunctioned, the braking system
remains available with full brake boosting
effect. However, the rear wheels can still lock,
e.g. under full braking. This could cause you
to lose control of your vehicle and cause an
accident. You should therefore adapt your
driving style to the different handling
characteristics.
XObserve the notes on warning and indicator
lamps ( Y page 242) as well as display
messages ( Y page 216).
ADAPTIVE BRAKE
ADAPTIVE BRAKE enhances braking safety
and offers increased braking comfort. In
addition to the braking function, ADAPTIVE
BRAKE also has the HOLD function
( Y page 172) and hill start assist
( Y page 140). For further information, see
Driving tips ( Y page 156).
64Driving safety systemsSafety

PRE-SAFE®
Brake
PRE-SAFE ®
Brake is only available in vehicles
with DISTRONIC PLUS.
i Observe the "Important safety notes"
section ( Y page 59).
PRE-SAFE ®
Brake can help you to minimize
the risk of a frontal collision with a vehicle
ahead or reduce the effects of such a
collision. If PRE-SAFE ®
Brake has detected a
risk of collision, you will be warned visually
and acoustically as well as by automatic
braking. PRE-SAFE ®
Brake cannot prevent a
collision without your intervention.
At speeds above approximately
20 mph (30 km/h), this function warns you
when you are rapidly approaching the vehicle
in front. An intermittent warning tone will
then sound and the · distance warning
lamp in the instrument cluster will light up.XBrake immediately in order to increase the
distance from the vehicle in front.
or
XTake evasive action provided it is safe to do
so.
If the driver and front passenger have their
seat belt fastened, PRE-SAFE ®
Brake can also
brake the vehicle automatically at speeds
from approximately 20 mph (30 km/h) to
approximately 124 mph (200 km/h).
Due to the nature of the system, particularly
complicated driving conditions may cause
unnecessary warnings or the unnecessary
intervention of PRE-SAFE ®
Brake. To stop the
braking action, you can either depress the
accelerator pedal further, activate kickdown
or release the brake pedal.
The braking action of PRE-SAFE ®
Brake is
ended automatically if:
R your speed drops below approximately
9 mph (15 km/h).
R you maneuver to avoid the obstacle.
Rthere is no longer any danger of a rear-end
collision.
R there is no longer an obstacle detected in
front of your vehicle.
i USA only: this device has been approved
by the FCC as a "Vehicular Radar System".
The radar sensor is intended for use in an
automotive radar system only. Removal,
tampering, or altering of the device will void
any warranties, and is not permitted by the
FCC. Do not tamper with, alter, or use in
any non-approved way.
Any unauthorized modification to this
device could void the user's authority to
operate the equipment.
i Canada only: this device complies with
RSS-210 of Industry Canada. Operation is
subject to the following two conditions:
1. This device may not cause interference,
and
2. this device must accept any interference
received, including interference that may
cause undesired operation of the device.
Removal, tampering, or altering of the
device will void any warranties, and is not
permitted. Do not tamper with, alter, or use
in any non-approved way.
Any unauthorized modification to this
device could void the user's authority to
operate the equipment.
With the help of the radar sensor system,
PRE-SAFE ®
Brake can detect obstacles that
are in front of your vehicle for an extended
period of time.
At speeds up to approximately 40 mph
(70 km/h), PRE-SAFE ®
Brake can also react
to stationary obstacles, for example stopped
or parked vehicles.
If you approach an obstacle and PRE-SAFE ®
Brake detects a risk of collision, the system
will initially alert you both visually and
acoustically. If you do not brake or take
evasive action, the system will warn you by
automatically braking the vehicle gently. If
the risk of collision remains and you do notDriving safety systems65SafetyZ

brake, take evasive action or accelerate
significantly, the vehicle may perform
automatic emergency braking. Automatic
emergency braking is not performed until
immediately prior to an accident that can no
longer be avoided.GWARNING
Even if PRE-SAFE ®
Brake slows the vehicle
before an imminent rear-end collision, the
system cannot avert a collision without the
intervention of the driver. There is a risk of an
accident. Brake according to the situation or
take evasive action. Delayed intervention by
the driver can lead to an accident.
GWARNING
PRE-SAFE ®
Brake cannot always detect
complex traffic situations properly.
In these cases, PRE-SAFE(R) Brake may:
R give an unnecessary warning and then
brake the vehicle
R neither give a warning nor intervene
There is a risk of an accident. Always pay
particular attention to the traffic situation and
be ready to brake, especially if PRE-SAFE(R)
Brake warns you. Terminate the intervention
in a non-critical driving situation.
In particular, the detection of obstacles can
be impaired if there is:
R dirt on the sensors or anything else
covering the sensors
R snow or heavy rain
R interference by other radar sources
R the possibility of strong radar reflections,
for example in parking garages
R a narrow vehicle traveling in front, e.g. a
motorbike
R a vehicle traveling in front on a different line
GWARNING
PRE-SAFE ®
Brake does not react:
R to people or animals
R to oncoming vehicles
R
to crossing traffic
R in curves
As a result, PRE-SAFE ®
Brake cannot
intervene in critical situations. There is a risk
of an accident. Always pay careful attention
to the traffic situation and be ready to brake.
In order to maintain the appropriate distance
to the vehicle in front and thus prevent a
collision, you must apply the brakes yourself.XTo activate/deactivate: activate or
deactivate PRE-SAFE ®
Brake in the on-
board computer ( Y page 205).
The Ä symbol appears in the
multifunction display as long as the HOLD
function is not activated ( Y page 172).
On vehicles with Parking Guidance, the
Ä symbol is displayed when
transmission position P is selected or if you
drive faster than 22 mph (35 km/h).
For PRE-SAFE ®
Brake to assist you when
driving, the radar sensor system must be
switched on ( Y page 208) and operational.
Following damage to the front end of the
vehicle, have the configuration and operation
of the radar sensors checked at a qualified
specialist workshop. This also applies to
collisions at low speeds where there is no
visible damage to the front of the vehicle.
Theft deterrent locking systems
Immobilizer
The immobilizer prevents your vehicle from
being started without the correct SmartKey.
When leaving the vehicle, always take the
SmartKey with you and lock the vehicle. The
engine can be started by anyone with a valid
SmartKey that is left inside the vehicle.
XTo activate with the SmartKey: remove
the SmartKey from the ignition lock.XTo activate with KEYLESS-GO: switch the
ignition off and open the driver's door.XTo deactivate: switch on the ignition.66Theft deterrent locking systemsSafety

Useful information
i This Operator's Manual describes all
models and all standard and optional
equipment of your vehicle available at the
time of publication of the Operator's
Manual. Country-specific differences are
possible. Please note that your vehicle may
not be equipped with all features
described. This also applies to safety-
related systems and functions.
i Please read the information on qualified
specialist workshops ( Y page 24).
SmartKey
Important safety notes
GWARNING
When leaving the vehicle, always remove the
SmartKey from the ignition lock. Always take
the SmartKey with you and lock the vehicle.
Do not leave children unsupervised in the
vehicle, even if they are secured in a child
restraint system, and do not give them access
to an unlocked vehicle. A child's unsupervised
access to a vehicle could result in an accident
and/or serious personal injury. They could:
R injure themselves on vehicle parts
R be seriously or fatally injured by extreme
heat or cold
R injure themselves or have an accident with
vehicle equipment that may still be in
operation even after the SmartKey has
been removed from the ignition, such as the
seat adjustment, steering wheel
adjustment or memory function.
If children open a door, they could cause
severe or even fatal injury to other persons; if
they get out of the vehicle, they could injure
themselves when doing so or be seriously or
even fatally injured by any passing traffic.
Do not expose the child restraint system to
direct sunlight. The child restraint system's
metal parts, for example, could become very
hot, and a child could be burned on these
parts.GWARNING
If a key ring is too heavy or too large, the
weight acting on the SmartKey could cause it
to turn in the ignition lock or catch on the
steering wheel. This could cause the engine
to be switched off suddenly. You could lose
control of the vehicle and cause an accident.
Do not attach any heavy or large key rings to
the SmartKey that is inserted in the ignition.
General notes
If you cannot lock or unlock the vehicle with
the SmartKey, either the battery in the
SmartKey is discharged, the SmartKey is
faulty or the starter battery is discharged.
XCheck the battery in the SmartKey and
replace it if necessary ( Y page 74).XUnlock the driver's door using the
mechanical key ( Y page 79).XLock the vehicle using the mechanical key
( Y page 79).XHave the starter battery and the battery
contacts checked at a qualified specialist
workshop.
If the SmartKey is faulty, contact Roadside
Assistance or a qualified specialist workshop.
SmartKey functions
General notes
i USA only:
This device complies with Part 15 of the
FCC Rules. Operation is subject to the
following two conditions:
1. This device may not cause harmful
interference, and
2. this device must accept any interference
received, including interference that may
cause undesired operation.
70SmartKeyOpening/closing

Removing the mechanical keyXPush release catch : in the direction of
the arrow and at the same time, remove
mechanical key ; from the SmartKey.
SmartKey battery
Important safety notes
Have the batteries changed at a qualified
specialist workshop.
GWARNING
Batteries contain toxic substances.
Swallowing batteries can lead to serious
health issues or death.
Keep batteries out of the reach of children.
Seek medical attention immediately if a
battery is swallowed.
GWARNING
The SmartKey batteries contain perchlorate
material, which may require special handling
and regard for the environment. Observe
government disposal guidelines. California
residents, see www.dtsc.ca.gov/
HazardousWaste/Perchlorate/
index.cfm .
Checking the batteryXPress the & or % button.
The battery is working properly if battery
check lamp : lights up briefly
If battery check lamp : does not light up
briefly during the test, the battery is
discharged.
XChanging the battery ( Y page 74)
i
You can obtain the battery at a qualified
specialist workshop.
i If the SmartKey battery is checked within
the signal reception range of the vehicle,
pressing the & or % button locks or
unlocks the vehicle.
Changing the battery
You require a CR 2025 3 V cell battery.
XTake the mechanical key out of the
SmartKey ( Y page 73).XPress mechanical key ; into the opening
in the SmartKey in the direction of the74SmartKeyOpening/closing

ProblemPossible causes/consequences and M SolutionsThe engine cannot be
started using the
SmartKey.The on-board voltage is too low.XSwitch off non-essential consumers, e.g. seat heating or interior
lighting, and try to start the engine again.
If this does not work:
XCheck the starter battery and charge it if necessary
( Y page 298).
or
XJump-start the vehicle ( Y page 301).
or
XConsult a qualified specialist workshop.The engine cannot be
started using the
SmartKey.The steering lock is mechanically blocked.XRemove the SmartKey and reinsert it into the ignition lock. While
doing this, turn the steering wheel in both directions.The engine cannot be
started using KEYLESS-
GO. The SmartKey is in
the vehicle.A door is open. Therefore, the SmartKey cannot be detected as
easily.XClose the door and try to start the vehicle again.There is interference from a powerful source of radio waves.XStart your vehicle with the SmartKey in the ignition lock.Doors
Important safety notes
GWARNING
When leaving the vehicle, always remove the
SmartKey from the ignition lock. Always take
the SmartKey with you and lock the vehicle.
Do not leave children unsupervised in the
vehicle, even if they are secured in a child
restraint system, and do not give them access
to an unlocked vehicle. A child's unsupervised
access to a vehicle could result in an accident
and/or serious personal injury. They could:
R injure themselves on vehicle parts
R be seriously or fatally injured by extreme
heat or cold
R injure themselves or have an accident with
vehicle equipment that may still be in
operation even after the SmartKey has
been removed from the ignition, such as the
seat adjustment, steering wheel
adjustment or memory function.
If children open a door, they could cause
severe or even fatal injury to other persons; if
they get out of the vehicle, they could injure
themselves when doing so or be seriously or
even fatally injured by any passing traffic.
Do not expose the child restraint system to
direct sunlight. The child restraint system's
metal parts, for example, could become very
hot, and a child could be burned on these
parts.GWARNING
Do not carry heavy or hard objects in the
passenger compartment or trunk unless they
are firmly secured in place.
Doors77Opening/closingZ