sensor MERCEDES-BENZ R-Class 2012 W251 Owner's Guide

GWARNING
Blind Spot Assist monitors certain areas in the
immediate vicinity of your vehicle. Vehicles
that approach and drive past at high speeds
are not detected. There is no display and no
warning.
If the lanes are very wide, it may not be
possible to monitor the complete width of the
neighboring lane. For this reason, vehicles in
the next lane may not be detected, especially
if they are driving in a staggered formation.
This may be the case if vehicles are driving at
that edge of their lane which is furthest away
from your vehicle.
Always pay attention to traffic conditions and
your surroundings. Otherwise, you may fail to
recognize dangers in time, cause an accident
and injure yourself and others.
If the lanes are narrow, vehicles driving in the
lane beyond the lane next to your vehicle may
be indicated, especially if the vehicles are not
driving in the middle of their lane. This may
be the case if the vehicles are driving on the
inner side of their lane.
Due to the nature of the system:
R warnings may be issued in error when
driving close to crash barriers or similar
solid lane borders.
R warnings may be interrupted when driving
alongside particularly long vehicles, for
example trucks, for a prolonged time.
The two sensors for Blind Spot Assist are
integrated into the sides of the rear bumper.
Make sure that the bumper is free from dirt,
ice or slush around the sensors. The radar
sensors must not be covered, for example by
bicycle racks or overhanging cargo. Following
a severe impact or in the event of damage to
the bumpers, have the function of the radar
sensors checked at a qualified specialist
workshop, such as an authorized Mercedes-
Benz Center. Blind Spot Assist may otherwise
not work properly.
Indicator and warning display:Yellow indicator lamp/red warning lamp
When Blind Spot Assist is activated, indicator
lamp : lights up yellow in the exterior
mirrors up to a vehicle speed of 20 mph
(30 km/h). When the vehicle speed exceeds
20 mph (30 km/h), the indicator lamp goes
out and Blind Spot Assist is ready for use.
When your speed exceeds approximately
20 mph (30 km/h), warning lamp : lights up
red on the corresponding side whenever a
vehicle is detected in the blind spot
monitoring range. This warning is always
given when a vehicle enters the blind spot
monitoring range from behind or from the
190Driving systemsDriving and parking

side. When you are passing another vehicle,
the warning is emitted only if the difference
in speed is less than 7 mph (12 km/h).
The yellow indicator lamp goes out if the
reverse gear is engaged. In this event, Blind
Spot Assist is no longer active.
The brightness of the indicator/warning
lamps is adjusted automatically according to
the ambient light.GWARNING
Blind Spot Assist is not active at speeds under
approximately 20 mph (30 km/h). The
indicator lamps in the exterior mirrors are
yellow. Vehicles in the monitoring range are
then not indicated.
Always pay attention to traffic conditions and
your surroundings. Otherwise, you may fail to
recognize dangers in time, cause an accident
and injure yourself and others.
Collision warning
If a vehicle is detected in the monitoring range
of Blind Spot Assist and you switch on the turn
signal, a double warning tone sounds. Red
warning lamp : flashes. If the turn signal
remains on, detected vehicles are indicated
by the flashing of red warning lamp :. There
are no further warning tones.
Switching on Blind Spot Assist
XMake sure that the radar sensor system
( Y page 208) and Blind Spot Assist
( Y page 210) are activated in the on-board
computer.XTurn the SmartKey to position 2 in the
ignition lock.
Warning lamps : light up red in the
exterior mirrors for approximately 1.5
seconds and then turn yellow.
Trailer towing
When you attach a trailer, make sure you have
correctly established the electrical
connection. This can be accomplished by
checking the trailer lighting. In this event,
Blind Spot Assist is deactivated. The indicator
lamp in the exterior mirrors lights up yellow
and the Blind Spot Assist Currently
Unavailable See Operator's Manual
message appears in the multifunction
display.
i You can deactivate the indicator lamps in
the exterior mirrors.
To do so, switch off Blind Spot Assist when:
R the SmartKey is in position 2 in the
ignition lock.
R the engine is not running.
R the electrical connection to the trailer
has been established.
Trailer towing
Notes on towing a trailer
Important safety notes
GWARNING
When towing a trailer, incorrect equipment
and driving style could cause you to lose
control of the vehicle.
Towing incorrectly or not observing this
Operator's Manual could lead to damage to
the vehicle and/or serious injuries. Observe
the following guidelines to ensure safe trailer
towing.
Contact a Mercedes-Benz Center if you need
further explanation of the information
contained in this Operator's Manual.
General information
R Only install an approved trailer coupling on
your vehicle.
Further information on availability and on
installation is available from any authorized
Mercedes-Benz Center.
R The bumpers of your vehicle are not
suitable for installing detachable trailer
couplings.
Trailer towing191Driving and parkingZ

XBefore leaving the vehicle, turn the
SmartKey to position 0 in the ignition lock.XTurn the SmartKey to position 2 in the
ignition lock and back to position 0.
The delayed switch-off is deactivated.
Delayed switch-off is reactivated the next
time you start the engine.
Activating/deactivating the interior
lighting delayed switch-off
If the Interior lighting Delayed Shut-
off function is activated and you remove the
SmartKey from the ignition lock, the interior
lighting remains on for 10 seconds.
XPress the V or U button on the
steering wheel to select the Settings
menu.XPress the & button to select submenus.XPress the W or X button to select the
Lighting submenu.XPress the & button to select Interior
Lighting Delayed Shut-off .XPress the W or X button to activate
or deactivate the Interior Lighting
Delay function.XPress the &, V or U button to
select a different display.
Vehicle
Activating/deactivating the automatic
door locking feature
If you select the Automatic Door Locking
function, the vehicle is centrally locked above
a speed of around 9 mph (15 km/h).
i For further information on the automatic
locking feature, see ( Y page 80).
XPress the V or U button on the
steering wheel to select the Settings
menu.XPress the & button to call up the
selection of submenus.XPress the W or X button to select the
Vehicle submenu.XPress the & button to select
Automatic Door Locking .XPress the W or X button to switch
Automatic Door Locking on or off.XPress the &, V or U button to
select a different display.
Activating/deactivating the acoustic
locking confirmation
If you activate the Acoustic Lock
Feedback function, an audible signal sounds
when the vehicle is locked or unlocked. When
unlocking, the signal sounds once. When
locking, it sounds three times.
XPress the V or U button on the
steering wheel to select the Settings
menu.XPress the & button to call up the
selection of submenus.XPress the W or X button to select the
Vehicle submenu.XPress the & button to select Acoustic
Lock Feedback .XPress the W or X button to switch
the Acoustic Lock Feedback function on
or off.XPress the &, V or U button to
select a different display.
Activating/deactivating the radar sensor
system
If the radar sensor system is switched off,
Blind Spot Assist (Y page 189) is deactivated.
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 nonapproved way.
Any unauthorized modification to this
device could void the user's authority to
operate the equipment.
208Menus and submenusOn-board computer and displays

iCanada only:
This device complies with RSS-210 of
Industry Canada. 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.
Any unauthorized modification to this
device could void the user's authority to
operate the equipment.XPress the V or U button on the
steering wheel to select the Settings
menu.XPress the & button to select submenus.XPress the W or X button to select the
Vehicle submenu.XPress the & button to select Radar
Sensor (See Operator's Manual) .XPress the W or X button to activate
or deactivate the Radar Sensor (see
Operator's Manual) .XPress the &, V or U button to
select a different display.
Convenience
Activating/deactivating the EASY-
ENTRY/EXIT feature
You can use the Easy-entry Function to
activate or deactivate the EASY-ENTRY/EXIT
feature ( Y page 108).
GWARNING
You must make sure no one can become
trapped or injured by the moving steering
wheel when the easy-entry/exit feature is
activated.
To stop steering wheel movement do one of
the following:
R Move steering wheel adjustment stalk.
R Press one of the memory position buttons.
R Press memory button M.
Do not leave children unattended in the
vehicle, or with access to an unlocked vehicle.
Children could open the driver's door and
unintentionally activate the easy-entry/exit
feature, which could result in an accident
and/or serious personal injury.XPress the V or U button on the
steering wheel to select the Settings
menu.XPress the & button to select submenus.XPress the W or X button to select the
Comfort submenu.XPress the & button to select Easy-
entry Function .XPress the W or X button to activate
or deactivate the Easy-entry Function .XPress the &, V or U button to
select a different display.
Switching the belt adjustment on/off
For further information on belt adjustment
( Y page 54).
XPress the V or U button on the
steering wheel to select the Settings
menu.XPress the & button to select submenus.XPress the W or X button to select the
Comfort submenu.XPress the & button to select Belt
Adjustment .XPress the W or X button to activate
or deactivate Belt Adjustment .XPress the &, V or U button to
select a different display.
Switching the Fold in mirrors when
locking function on/off
If you activate the Fold In Mirrors When
Locking function, the exterior mirrors are
folded in when the vehicle is locked. If you
switch on the ignition, the exterior mirrors
fold out again.
Menus and submenus209On-board computer and displaysZ

Display messagesPossible causes/consequences and M Solutionsb
AUTO Light
InoperativeThe light sensor is defective.XVisit a qualified specialist workshop.
USA only:
XSwitch off the daytime running lamps in the on-board computer
( Y page 206).XSwitch the lights on and off using the light switch.b
Switch Off LightsThe lights are still switched on when you leave the vehicle. A
warning tone also sounds.XTurn the light switch to $ or à .
or
XIf the rear fog lamp is switched on: press the light switch in to
the stop.
Engine
Display messagesPossible causes/consequences and M Solutions+
Top Up Coolant See
Operator's ManualThe coolant level is too low.XAdd coolant, observing the warning notes when doing so
( Y page 285).XIf the coolant needs to be refilled more often than usual, have
the engine coolant system checked at a qualified specialist
workshop.GWARNING
Do not spill antifreeze on hot engine parts. Antifreeze contains ethylene glycol which may burn
if it comes into contact with hot engine parts. You could be seriously burned.
! The coolant level is too low. Avoid making long journeys with too little coolant in the cooling
system. The engine will otherwise be damaged.
The display messages and the corresponding symbol that indicate that the coolant level is
too low must not be ignored.
Display messages225On-board computer and displaysZ

Display messagesPossible causes/consequences and M SolutionsBlind Spot Assist
Currently
Unavailable, See
Operator's ManualBlind Spot Assist is temporarily inoperative if:
R the sensors are dirty.
R its function is impaired due to heavy rain or snow.
R the radar sensor system is outside the operating temperature
range.
R the radar sensor system is temporarily inoperative, e.g. due to
electromagnetic radiation emitted by nearby TV or radio
stations or other sources of electromagnetic radiation.
The yellow 9 indicator lamps also light up in the exterior
mirrors.
Blind Spot Assist is operational again and the display message
disappears if:
R the dirt (e.g. slush) drops away while the vehicle is in motion.
R the system detects that the sensors are fully available again.
R the radar sensor system is back within the operating
temperature range.
If the display message continues to be displayed:XClean the sensors ( Y page 291).XRestart the engine.Blind Spot Assist
InoperativeBlind Spot Assist is defective.
The yellow 9 indicator lamps also light up in the exterior
mirrors.XVisit a qualified specialist workshop.Cruise Control
InoperativeCruise control is defective.XVisit a qualified specialist workshop.Cruise Control
--- MPH A condition for activating cruise control has not been fulfilled.
You attempted to save a speed of less than 20 mph (30 km/h).XIf the situation allows, drive faster than 20 mph ( 30 km/h) and
save the speed.XCheck the activation conditions for cruise control
( Y page 170).DISTRONIC
--- MPH An activation condition for DISTRONIC is not fulfilled.XCheck the activation conditions for DISTRONIC ( Y page 173).DISTRONIC
OverrideDISTRONIC is no longer controlling the speed of the vehicle.XTake your foot off the accelerator pedal.230Display messagesOn-board computer and displays

Display messagesPossible causes/consequences and M SolutionsDISTRONIC
InoperativeDISTRONIC is defective or the display has failed.XVisit a qualified specialist workshop.DISTRONIC
Currently
Unavailable See
Operator's ManualDISTRONIC is deactivated and is temporarily inoperative if:
R the DISTRONIC cover in the radiator grill is dirty.
R its function is impaired due to heavy rain, snow or fog.
R the radar sensor system is temporarily inoperative, e.g. due to
electromagnetic radiation emitted by nearby TV or radio
stations or other sources of electromagnetic radiation.
R the radar sensor system has not detected any vehicles or
stationary objects, e.g. traffic signs, for a long time.
R the system is outside the operating temperature range.
DISTRONIC becomes available again and the display message
disappears if:
R the dirt (e.g. slush) drops away while the vehicle is in motion.
R the system detects that the sensors are fully available again.
R the system is within the operating temperature range.
If the display message continues to be displayed:XClean the DISTRONIC cover in the radiator grill ( Y page 291).XRestart the engine.GWARNING
DISTRONIC cannot take weather conditions into account. Switch off DISTRONIC or do not turn
it on if the sensor is dirty or visibility is diminished as a result of snow, rain or fog. The distance
control may be impaired even before the system is able to detect a dirty sensor. The DISTRONIC
Currently Unavailable See Operator's Manual message will be displayed in the
multifunction display and DISTRONIC will be turned off.
Tires
GWARNING
Do not drive with a flat tire. A flat tire affects the ability to steer or brake the vehicle. You may
lose control of the vehicle. Continued driving with a flat tire will cause excessive heat build-up
and possibly a fire.
GWARNING
Follow recommended tire inflation pressures.
Do not underinflate tires. Underinflated tires wear excessively and/or unevenly, adversely affect
handling and fuel economy, and are more likely to fail from being overheated.
Display messages231On-board computer and displaysZ

Do not overinflate tires. Overinflated tires can adversely affect handling and ride comfort, wear
unevenly, increase stopping distance, and result in sudden deflation (blowout) because they are
more likely to become punctured or damaged by road debris, potholes etc.Display messagesPossible causes/consequences and M SolutionsTire Pressure
Check TiresGRisk of accident
The tire pressure loss warning system has detected a significant
loss in pressure.
XStop the vehicle without making any sudden steering or braking
maneuvers. Pay attention to the traffic conditions as you do so.XCheck the tires and, if necessary, change the wheel
( Y page 346).XCheck the tire pressures and, if necessary, set to the correct
tire pressure.XRestart the tire pressure loss warning system when the tire
pressure is correct ( Y page 329).Check tires,
then restart Run
Flat IndicatorThe tire pressure loss warning system generated a display
message and has not been restarted since.XSet the correct tire pressure in all four tires.XRestart the tire pressure loss warning system ( Y page 329).Run Flat Indicator
InoperativeThe tire pressure loss warning system is defective.XVisit a qualified specialist workshop.Tire pressure
displayed after
driving for a few
minutesThe tire pressure monitor is measuring the tire pressure.XDrive on.
The tire pressures appear in the multifunction display after you
have been driving for a few minutes.Tire Pressure
Monitor
InoperativeThe tire pressure monitor is defective.XVisit a qualified specialist workshop.Tire Pressure
Monitor
Inoperative No
Wheel SensorsThe wheels mounted do not have a suitable tire pressure sensor.
The tire pressure monitor is deactivated.XMount wheels with suitable tire pressure sensors.
The tire pressure monitor is activated automatically after driving
for a few minutes.232Display messagesOn-board computer and displays

Display messagesPossible causes/consequences and M SolutionsCheck
Tire(s)GRisk of accident
The tire pressure in one or more tires has dropped significantly.
The wheel position is displayed in the multifunction display.
XStop the vehicle without making any sudden steering or braking
maneuvers. Pay attention to the traffic conditions as you do so.XCorrect the tire pressure ( Y page 331).XIf necessary, change a wheel ( Y page 346).Caution:
Tire DefectGRisk of accident
The tire pressure in one or more tires has dropped suddenly. The
wheel position is displayed in the multifunction display.
XStop the vehicle without making any sudden steering or braking
maneuvers. Pay attention to the traffic conditions as you do so.XIf necessary, change a wheel ( Y page 346).Tire Pressure(s)
Please CorrectThe tire pressure is too low in at least one of the tires or the tire
pressure difference between the wheels is too great.XCheck the tire pressures at the next opportunity. If necessary,
correct the tire pressure ( Y page 331).XRestart the tire pressure monitor ( Y page 333).Tire Pressure
Monitor
Wheel Sensor
MissingThere is no signal from the tire pressure sensor of one or several
wheels. The pressure of the affected tire is not displayed in the
multifunction display.XHave the defective tire pressure sensor replaced at a qualified
specialist workshop.Tire Pressure
Monitor
Currently
UnavailableDue to a source of radio interference, no signals can be received
from the wheel sensors. The tire pressure monitor is temporarily
malfunctioning.XDrive on.
The tire pressure monitor restarts automatically as soon as the
problem has been solved.h
Tire Pressure
Caution: Tire
DefectGRisk of accident
The tire pressure in one or more tires has dropped suddenly.
XStop the vehicle without making any sudden steering or braking
maneuvers. Pay attention to the traffic conditions as you do so.XIf necessary, change a wheel ( Y page 346).Display messages233On-board computer and displaysZ

therefore, only use products that have been
tested and approved by Mercedes-Benz.
Information on tested and approved
products can be obtained at any authorized
Mercedes-Benz Center or on the Internet at
http://www.mbusa.com (USA only).GWARNING
Washer solvent/antifreeze is highly
flammable. Do not spill washer solvent/
antifreeze on hot engine parts, because it may
ignite and burn. You could be seriously
burned.
! At temperatures below freezing: always
fill the washer fluid reservoir with a mix of
water and windshield washer concentrate
(e.g. MB WinterFit). There is otherwise a
risk of damaging the windshield washer
system/headlamp cleaning system.
! Only use washer fluid concentrate which
is suitable for plastic lenses. Unsuitable
washer fluid concentrate could damage the
plastic lenses of the headlamps.
! Do not add distilled or de-ionized water to
the washer fluid container. Otherwise, the
level sensor may be damaged.
i Add windshield washer concentrate, e.g.
MB SummerFit, to the washer fluid all year
round.
Example: washer fluid reservoir
XMix the windshield washer fluid in a
container beforehand.XAt temperatures above freezing: fill the
washer fluid reservoir with a mix of waterand windshield washer concentrate (e.g.
MB SummerFit).XAt temperatures below freezing: fill the
washer fluid reservoir with a mix of water
and windshield washer concentrate (e.g.
MB WinterFit). Adapt the mixing ratio to the
outside temperature. For information on
the mixing ratio ( Y page 360).XTo open: pull cap : upwards by the tab.XAdd the premixed washer fluid.XTo close: press cap : onto the filler neck
until it engages.
Brake fluid level
! If you notice that the brake fluid level in
the brake fluid reservoir has fallen to the
MIN mark or less, check the brake system
immediately for leaks. Also check the
thickness of the brake linings. Contact a
qualified specialist workshop, e.g. an
authorized Mercedes-Benz Center
immediately.
Do not add brake fluid. This does not
correct the error.
Only check the brake fluid level when the
vehicle is stationary and on a level surface.
The brake fluid level is correct if it is between
MIN marking ; and MAX marking : on the
brake fluid reservoir.
286Engine compartmentMaintenance and care