2012 MERCEDES-BENZ C-Class SEDAN replace key

If the SmartKey has been removed from the
ignition lock or is in position 0, indicator lamp
45 : does not light up.
GWARNING
If the red 6 SRS warning lamp in the
instrument cluster and the 45
indicator lamp light up simultaneously, the
OCS is malfunctioning. The front passenger
front air bag will be deactivated in this case.
Have the system checked by qualified
technicians as soon as possible. Contact an
authorized Mercedes-Benz Center.
Only have the seat repaired or replaced at an
authorized Mercedes-Benz Center.
In order to ensure proper operation of the air
bag system and OCS:
R Sit with the seat belt properly fastened in a
position that is as upright as possible with
your back against the seat backrest.
R When seated, a passenger should not
position him/herself in such a way as to
cause the passenger's weight to be lifted
from the seat cushion as this may result in
the OCS being unable to correctly
approximate the passenger's weight
category.
R Read and observe all warnings in this
chapter.
System self-test
The 45 indicator lamp illuminates
when you:
R turn the SmartKey to position 1 or 2 in the
ignition lock
R on vehicles with KEYLESS-GO, press the
Start/Stop button once or twice
If an adult occupant is properly sitting on the
passenger seat and the OCS classifies the
occupant as an adult, the 45 indicator
lamp illuminates and goes out again after
approximately 6 seconds.
If the seat is not occupied and the OCS
classifies the front passenger seat as being
unoccupied, the 45 indicator lamp
will illuminate and not go out.
GWARNING
If the 4 5 indicator lamp does not
illuminate, the system is not functioning. You
must contact an authorized Mercedes-Benz
Center before seating any child on the front
passenger seat.
For more information, see "Problems with the
Occupant Classification System"
( Y page 46).
GWARNING
Never place anything between seat cushion
and child seat (e.g. a pillow), since it reduces
the effectiveness of the OCS. The underside
and rear side child restraint system must be
placed entirely on the seat cushion and the
backrest of the front-passenger seat
backrest.
If necessary, adjust the tilt of the passenger
seat backrest.
An incorrectly mounted child seat could cause
injuries to the child in case of an accident,
instead of increasing protection for the child.
Follow the manufacturer's instructions for
installation of child restraint systems.
Occupant safety45SafetyZ

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

Problems with the SmartKeyProblemPossible causes/consequences and M SolutionsYou cannot lock or
unlock the vehicle
using the SmartKey.The SmartKey battery is discharged or nearly discharged.XTry again to lock/unlock the vehicle using the remote control
function of the SmartKey. Point the tip of the SmartKey at the
driver's door handle from close range and press the %/
& button.
If this does not work:
XCheck the SmartKey battery ( Y page 74) and replace it if
necessary ( Y page 74).XLock ( Y page 79) or unlock ( Y page 79) the vehicle using
the mechanical key.The SmartKey is faulty.XLock ( Y page 79) or unlock ( Y page 79) the vehicle using
the mechanical key.XHave the SmartKey checked at a qualified specialist workshop.You can no longer lock
or unlock the vehicle
using KEYLESS-GO.There is interference from a powerful source of radio waves.XLock/unlock the vehicle using the remote control function of
the SmartKey. Point the tip of the SmartKey at the driver's door
handle from close range and press the %/& button.There is a malfunction with KEYLESS-GO.XLock/unlock the vehicle using the remote control function of
the SmartKey. Point the tip of the SmartKey at the driver's door
handle from close range and press the %/& button.XHave KEYLESS-GO checked at a qualified specialist workshop.
If this does not work:
XCheck the SmartKey battery ( Y page 74) and replace it if
necessary ( Y page 74).XLock ( Y page 79) or unlock ( Y page 79) the vehicle using
the mechanical key.You have lost a
SmartKey.XHave the SmartKey deactivated at a qualified specialist
workshop.XReport the loss immediately to the vehicle insurers.XIf necessary, have the locks changed as well.You have lost the
mechanical key.XReport the loss immediately to the vehicle insurers.XIf necessary, have the locks changed as well.76SmartKeyOpening/closing

Manual interior lighting controlXTo switch the front interior lighting on/
off: press the c button.XTo switch the rear interior lighting on/
off: press the u button.XTo switch the reading lamps on/off:
press the p button.
Crash-responsive emergency lighting
The interior lighting is activated automatically
if the vehicle is involved in an accident.
XTo switch off the crash-responsive
emergency lighting: press the hazard
warning lamp button.
or
XLock and then unlock the vehicle using the
SmartKey.
Replacing bulbs
Important safety notes
Xenon bulbs
If your vehicle is equipped with Xenon bulbs,
you can recognize this by the following: the
cone of light from the Xenon bulbs moves
from the top to the bottom and back again
when you start the engine. For this to be
observed, the lights must be switched on
before starting the engine.
GDANGER
Xenon bulbs carry a high voltage. You could
get an electric shock and be seriously or even
fatally injured if you touch the electric
contacts on Xenon bulbs. Therefore, never
remove the cover from Xenon bulbs.
Do not change Xenon bulbs yourself, but have
them replaced at a qualified specialist
workshop which has the necessary specialist
knowledge and tools to carry out the work
required.
Mercedes-Benz recommends that you use an
authorized Mercedes-Benz Center for this
purpose. In particular, work relevant to safety
or on safety-related systems must be carried
out at a qualified specialist workshop.
Bulbs and lamps are an important aspect of
vehicle safety. You must therefore make sure
that these function correctly at all times.
Have the headlamp setting checked regularly.
Other bulbs
There are bulbs other than the Xenon bulbs
that you cannot replace. Replace only the
bulbs listed (Y page 114). Have the bulbs that
you cannot replace yourself changed at a
qualified specialist workshop.
Mercedes-Benz recommends that you use an
authorized Mercedes-Benz Center for this
purpose. In particular, work relevant to safety
or on safety-related systems must be carried
out at a qualified specialist workshop.
If you require assistance changing bulbs,
consult a qualified specialist workshop.
Do not touch the glass tube of new bulbs with
your bare hands. Even minor contamination
can burn into the glass surface and reduce
the service life of the bulbs. Always use a lint-
free cloth or only touch the base of the bulb
when installing.
Only use bulbs of the correct type.
If the new bulb still does not light up, consult
a qualified specialist workshop.
Bulbs and lamps are an important aspect of
vehicle safety. You must therefore make sure
that these function correctly at all times.
Have the headlamp setting checked regularly.
GWARNING
Bulbs and lamps can be very hot. You should
therefore allow them to cool down before you
change them. Otherwise, you could be burned
if you touch them.
Keep bulbs out of the reach of children.
Otherwise, they could damage the bulbs, for
example, and injure themselves.
Replacing bulbs113Lights and windshield wipersZ

Replacing the wiper blades
Important safety notesGWARNING
For safety reasons, switch off the windshield
wipers and remove the key from the ignition
lock before changing the wiper blades
(vehicles with KEYLESS-GO: make sure that
the on-board electronics are in state 0).
Otherwise, the wiper motor could be switched
on suddenly and cause injury.
! To avoid damaging the wiper blades,
make sure that you touch only the wiper
arm of the wiper.
! Never open the hood if a windshield wiper
arm has been folded away from the
windshield.
Never fold a windshield wiper arm without
a wiper blade back onto the windshield.
Hold the windshield wiper arm firmly when
you change the wiper blade. If you release
the windshield wiper arm without a wiper
blade and it falls onto the windshield, the
windshield may be damaged by the force of
the impact.
Mercedes-Benz recommends that you have
the wiper blades replaced by a qualified
specialist workshop, e.g. at an authorized
Mercedes-Benz Center.
Replacing the windshield wiper blades
Removing the wiper blades
XRemove the SmartKey from the ignition
lock or turn it to position 0 (KEYLESS-GO).XFold the wiper arm away from the
windshield until it engages.XSet the wiper blade at right angles to the
wiper arm.XRemove the wiper blade from the retaining
pin on the wiper arm in the direction of the
arrow.
Installing the wiper blades
XPush the new wiper blade onto the
retaining pin on the wiper arm in the
opposite direction to the arrow.
Make sure that the wiper blade slides fully
onto the retaining pin on the wiper arm.XTurn the wiper blade parallel to the wiper
arm.XFold the wiper arm back onto the
windshield.
Replacing the rear window wiper blade
Removing the wiper blade
XRemove the SmartKey from the ignition
lock.XFold wiper arm : away from the rear
window until it engages.XPosition wiper blade ; at a right angle to
wiper arm :.118Windshield wipersLights and windshield wipers

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).
Overview of climate control systems
Important safety notes
GWARNING
Severe conditions (e.g. strong air pollution)
may require replacement of the filter before
its scheduled replacement interval. A clogged
filter will reduce the air volume to the interior
and the windows could fog up, impairing
visibility and endangering you and others.
Have a blocked filter replaced at a Mercedes-
Benz Center as soon as possible.
GWARNING
Follow the recommended settings for heating
and cooling given on the following pages.
Otherwise, the windows could fog up,
impairing visibility and endangering you and
others.
The automatic climate control adjusts the
temperature and the humidity of the vehicle
interior and filters undesired substances from
the air.
The automatic climate control is only
operational when the engine is running. 11
Optimum operation is only achieved if you
drive with the side windows and sliding
sunroof/panorama roof with power tilt/
sliding panel closed.
i Ventilate the vehicle for a brief period
during warm weather, e.g. using the
convenience opening feature ( Y page 84).
This will speed up the cooling process and
the desired vehicle interior temperature
will be reached more quickly.
i The integrated filter can filter out most
particles of dust and completely filters out
pollen. A clogged filter reduces the amount
of air supplied to the vehicle interior. For
this reason, you should always observe the
interval for replacing the filter, which is
specified in the Service Booklet. As it
depends on environmental conditions, e.g.
heavy air pollution, the interval may be
shorter than stated in the Service Booklet.
i It is possible that the residual heat
function may be activated automatically an
hour after the SmartKey is removed. The
vehicle is then ventilated for 30 minutes to
dry the air-conditioning system.11 Automatic climate control: the residual heat function can only be activated/deactivated when the ignition
is switched off.122Overview of climate control systemsClimate control

C 300 and C 300 Sport with automatic
transmission: you can tell a flexible fuel
vehicle by the label inside the fuel filler flap.
You can find more information under "Fuel"
( Y page 347), or by contacting an
authorized Mercedes-Benz Service Center
or visiting http://www.mbusa.com (USA
only).
Refueling
Fuel filler flap
The fuel filler flap is unlocked or locked
automatically when you open or close the
vehicle with the SmartKey or using KEYLESS-
GO.
The position of the fuel filler cap is displayed
in the instrument cluster 8. The arrow
next to the filling pump indicates the side of
the vehicle.
:To open the fuel filler flap;To insert the fuel filler cap=Tire pressure table?Fuel type
Opening
XSwitch off the engine.XRemove the SmartKey from the ignition
lock.
KEYLESS-GO: open the driver’s door. This
switches the ignition to position 0, which
corresponds to having removed theSmartKey. The driver’s door can be closed
again.XPress the fuel filler flap in the direction of
arrow :.
The fuel filler flap opens slightly.XOpen the fuel filler flap.XTurn the fuel filler cap counter-clockwise
and remove it.XInsert the fuel filler cap into the holder
bracket on the inside of filler flap ;.XCompletely insert the pump nozzle into the
filler neck and refuel.XOnly fill the tank until the pump nozzle
switches off.
! Overfilling the fuel tank could damage the
fuel system.
Closing
XReplace the fuel filler cap and turn it
clockwise. The fuel filler cap audibly
engages.XClose the fuel filler flap.
i If you drive with the fuel filler cap open,
reserve fuel warning lamp 8 flashes. In
addition, the ; Check Engine warning
lamp may light up. A message appears in
the multifunction display ( Y page 228).
For further information on warning and
indicator lamps in the instrument cluster,
see ( Y page 246).
i Close the fuel filler flap before locking the
vehicle. A locking pin otherwise prevents
the fuel filler flap from closing after the
vehicle has been locked.
Fuel filler flap emergency release
GWARNING
Avoid contact with the vehicle walls as they
may contain sharp edges. Otherwise, you
could injure yourself while releasing the fuel
filler flap.
Refueling151Driving and parkingZ

Limited braking performance on salt-
treated roadsGWARNING
The layer of salt on the brake discs and the
brake pads/linings may cause a delay in the
braking effect, resulting in a significantly
longer braking distance, which could lead to
an accident.
To avoid this danger, you should:
R occasionally brake carefully, without
putting other road users at risk, when you
are driving on salted roads. This helps to
remove any salt that may have started to
build up on the brake discs and the brake
pads/linings.
R maintain a greater distance to the vehicle
ahead and drive with particular care.
R carefully apply the brakes at the end of a
trip and immediately after commencing a
new trip, so that salt residues are removed
from the brake discs.
Servicing the brakes
! If the red brake warning lamp lights up in
the instrument cluster and you hear a
warning tone while the engine is running,
the brake fluid level may be too low.
Observe additional warning messages in
the multifunction display.
The brake fluid level may be too low due to
brake pad wear or leaking brake lines.
Have the brake system checked
immediately. This work should be carried
out at an authorized Mercedes-Benz
Center.
All checks and maintenance work on the
brake system must be carried out at a
qualified specialist workshop. This work
should be carried out at an authorized
Mercedes-Benz Center.
Have the brake pads replaced and the brake
fluid renewed at a qualified specialist
workshop, e.g. an authorized Mercedes-Benz
Center.
GWARNING
If brake pads or brake fluid other than those
recommended are used, the braking
properties of the vehicle can be degraded to
an extent that safe braking is substantially
impaired. This could result in an accident.
! Vehicles with 4MATIC: function or
performance tests may only be carried out
on a 2-axle dynamometer. If you are
planning to have the vehicle tested on such
a dynamometer, contact an authorized
Mercedes-Benz Center to obtain further
information first. Otherwise, you could
damage the drive train or the brake system.
! Vehicles with 4MATIC: as the ESP®
system operates automatically, the engine
and the ignition must be switched off
(SmartKey in position 0 or 1 in the ignition
lock or Start/Stop button in position 0 or
1 ) while the parking brake is being tested
on a brake dynamometer.
Braking maneuvers triggered automatically
by ESP ®
may seriously damage the brake
system.
! Vehicles with 4MATIC: as the ESP®
system operates automatically, the engine
and the ignition system must be switched
off (SmartKey in position 0 or 1 in the
ignition lock or Start/Stop button in
position 0 or 1) when:
R testing the parking brake on a brake
dynamometer.
R you intend to have the vehicle towed with
the front axle raised.
Braking maneuvers triggered automatically
by ESP ®
may seriously damage the brake
system.
If your brake system is subject only to
moderate loads, you should test the
functionality of your brakes at regular
intervals by pressing firmly on the brake pedal
at high speeds. This improves the grip of the
brake pads.
Driving tips157Driving and parkingZ