2012 MERCEDES-BENZ B-CLASS instrument cluster

Engine
Problem Possible causes/consequences and
M Solutions;
The yellow Check
Engine warning lamp
lights up while the
engine is running.
There may be a malfunction, for example:
R
in the engine management
R in the fuel injection system
R in the exhaust system
R in the ignition system
R in the fuel system
The emission limit values may be exceeded and the engine may
be running in emergency mode.
X Have the vehicle checked as soon as possible at a qualified
specialist workshop.
i In some states, you must immediately visit a qualified
specialist workshop as
soon as the yellow Check Engine warning
lamp lights up. This depends on the locally applicable legal
requirements. If in doubt, check whether such legal regulations
apply in the state in which you are currently driving. æ
The yellow reserve fuel
warning lamp lights up
while the engine is
running.
The fuel level has dropped into the reserve range.
X
Refuel at the nearest gas station. æ
The yellow reserve fuel
warning lamp flashes
while the engine is
running.
The fuel system pressure is too low. The fuel filler cap is not closed
correctly or the fuel system is leaking.
X
Check that the fuel filler cap is correctly closed.
X If the fuel filler cap is not correctly closed:
close the

fuel filler
cap.
X If the fuel filler cap is closed: visit a qualified specialist
workshop. ?
The red coolant
warning lamp lights up
while the engine is
running and
the

coolant
temperature gage is at
the start of the scale. The temperature sensor for the coolant temperature gage is
defective.
The coolant
temperature
is no longer being monitored. There is a
risk of engine damage if the coolant temperature is too high.
X Pull over and stop the vehicle safely and switch off the engine,
paying attention to

road and traffic conditions. Do not continue
driving under any circumstances.
X Secure the vehicle against rolling away ( Y page 149).
X Consult a qualified specialist workshop. Warning and indicator lamps in the instrument cluster
231
On-board computer and displays Z
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Problem Possible causes/consequences and
M Solutions?
The red coolant
warning lamp
comes
on
while the engine is
running. The coolant level is too low.
If the coolant level is correct, the airflow to the engine radiator
may be blocked or the electric engine radiator fan may be
malfunctioning.
The coolant is too hot and the engine is no longer being cooled
sufficiently.
X
Observe the additional display messages in the multifunction
display.
X Pull over and stop the vehicle safely and switch off the engine,
paying attention to road and traffic conditions.
X Secure the vehicle against rolling away ( Y page 149).
X Leave the vehicle and keep a safe distance from the vehicle until
the engine has cooled down.
X Check the coolant level and add coolant (Y page 269). Observe
the warning notes.
X If you need to add coolant more often than usual, have the
engine coolant system checked.
X Make sure that the air supply to the engine radiator is not
blocked, e.g. by snow, slush or ice.
X Do not start the engine again until the coolant temperature is
under

248 ‡
(120 †). Otherwise, the engine could be damaged.
X Drive to the nearest qualified specialist workshop.
X Avoid subjecting the engine to heavy loads, e.g. driving in
mountainous terrain, and stop-and-go traffic. ?
The red coolant
warning lamp
comes

on
while the engine is
running. A warning tone
also sounds. The coolant temperature has exceeded 248 ‡ (120 †). The
airflow
to the
engine radiator may be blocked or the coolant level
may be too low.
G WARNING
The engine is not being cooled sufficiently and may be damaged.
Do not drive
when your engine is overheated. This can cause some
fluids which may have leaked into the engine compartment to
catch fire.
Vapor from the overheated engine can also cause serious burns
which can occur just by opening the hood.
There is a risk of injury.
X Observe the additional display messages in the multifunction
display.
X Pull over and stop the vehicle safely and switch off the engine,
paying attention to road and traffic conditions.
X Secure the vehicle against rolling away ( Y page 149).232
Warning and indicator lamps in the instrument cluster
On-board computer and displays
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Problem Possible causes/consequences and
M SolutionsX
Leave the vehicle and keep a safe distance from the vehicle until
the engine has cooled down.
X Check the coolant level and add coolant (Y page 269). Observe
the warning notes.
X If you need to add coolant more often than usual, have the
engine coolant system checked.
X Make sure that the air supply to the engine radiator is not
blocked, e.g. by snow, slush or ice.
X At
coolant temperatures under 248 ‡ (120 †),
drive to the next
qualified specialist workshop.
X Avoid subjecting the engine to heavy loads, e.g. driving in
mountainous terrain, and stop-and-go traffic. Driving systems
Problem Possible causes/consequences and
M Solutions·
The red distance
warning lamp lights up
while the vehicle is in
motion. A
warning

tone
also sounds. You are approaching a vehicle or a stationary obstacle in your line
of travel at too high a speed.
X
Be prepared to brake immediately.
X Pay careful attention to the traffic situation. You may have to
brake or take evasive action. Warning and indicator lamps in the instrument cluster
233
On-board computer and displays Z
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Checking and adding other service
products
Checking coolant level G
WARNING
The engine cooling system is pressurized,
particularly when the engine is warm. When
opening the cap,
you could be scalded by hot
coolant spraying out. There is a risk of injury.
Let the engine cool down before opening the
cap. Wear eye and hand protection when
opening the cap. Open the cap slowly half a
turn to allow pressure to escape.
! The coolant may only be checked and
corrected when the engine is cool (coolant
temperature below 104 ‡ (40 †).
Checking the coolant when the coolant
temperature is above 104 ‡ (40 †) may
result in damage to the engine or to the
engine cooling system. Example
X
Park the vehicle on a level surface.
Only check the coolant level when the
vehicle is on

a level surface and the engine
has cooled down.
X Turn the SmartKey to position 2 in the
ignition lock (Y page 135).
X Check the coolant temperature display in
the instrument cluster.
The coolant temperature must be below
104 ‡ (40 †).
X Turn the SmartKey to position
0 (

Y page 135) in the ignition lock. X
Slowly turn cap : half a turn counter-
clockwise to allow excess pressure to
escape.
X Turn cap : further counter-clockwise
and
remove it.
If the coolant is at the level of marker bar
= in the filler neck when cold, there is
enough coolant in coolant expansion
tank ;.
X If necessary, add coolant that has been
tested and approved by Mercedes-Benz.
X Replace cap : and turn

it clockwise as far
as it will go.
For further information on coolant, see
(Y page 333).
Adding washer fluid to the windshield
washer system/headlamp cleaning
system G
WARNING
Windshield washer concentrate is highly
flammable. If it comes into contact with hot
engine components or the exhaust system it
could ignite. There is a risk of fire and injury.
Make sure that no windshield washer
concentrate is spilled next to the filler neck. Example
X
To open: pull cap : upwards by the tab.
X Add the premixed washer fluid.
X To close:
press cap :
onto the filler neck
until it engages. Engine compartment
269
Maintenance and care Z
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X
Press on/off switch ? on the tire inflation
compressor to ON.
The tire inflation compressor is switched
on. The tire is inflated.
i First, tire sealant is pumped into the tire.
The pressure can briefly rise to
approximately 500 kPa (5 bar/73 psi).
Do not switch off the tire inflation
compressor during this phase.
X Let the tire inflation compressor run for a
maximum of ten minutes. The tire should
then have attained a pressure of at least
200 kPa (2.0 bar/29 psi).
! Do not operate the tire inflation
compressor for longer than ten minutes at
a time without a break. It may otherwise
overheat.
The tire inflation compressor can be
operated again once it has cooled down.
If a pressure

of 200 kPa (2.0 bar/29 psi) has
been attained after a maximum of after ten
minutes, see ( Y page 284).
If a pressure of 200 kPa (2.0 bar/29 psi) has
not been attained after a maximum of ten
minutes, see ( Y page 284).
i If tire sealant leaks out, allow it to dry. It
can then be removed like a layer of film.
If your clothes are soiled with tire sealant,
have them cleaned with perchloroethylene
at a dry cleaner as soon as possible.
Tire pressure not reached If a pressure of 200 kPa (
2.0 bar
/29 psi) has
not been achieved after ten minutes:
X Switch off the tire inflation compressor.
X Unscrew the filler hose from the valve of
the faulty tire.
X Very slowly drive forwards or reverse
approximately 30 ft (10 m).
X Pump up the tire again.
After a maximum of ten minutes, the tire
pressure

must be
at least 200 kPa (2.0 bar/
29 psi). G
WARNING
If the required tire pressure is not reached
after the specified time, the tire is too badly
damaged. The tire sealant cannot repair the
tire in this

instance. Damaged tires and a tire
pressure that is too low can significantly
impair the vehicle's braking and driving
characteristics. There is a risk of accident.
Do not continue driving. Contact a qualified
specialist workshop.
Tire pressure reached G
WARNING
A tire temporarily sealed with tire sealant
impairs the driving characteristics and is not
suitable for higher speeds. There is a risk of
accident.
You should therefore adapt your driving style
accordingly and drive

carefully. Do not exceed
the specified maximum speed with a tire that
has been repaired using tire sealant.
! After use, excess tire sealant may run out
of the filler hose. This could cause stains.
Therefore, place the filler hose in the plastic
bag that contained the TIREFIT kit. H
Environmental note
Have the used tire sealant bottle disposed of
professionally, e.g. at a qualified specialist
workshop.
If a tire

pressure of 200 kPa (2.0 bar/29 psi)
has been achieved after ten minutes:
X Switch off the tire inflation compressor.
X Unscrew the filler hose from the valve of
the faulty tire.
X Stow the tire sealant bottle and the tire
inflation compressor.
X Pull away immediately.
The maximum speed for a tire sealed with tire
sealant is 50 mph (

80 km/h). The upper part
of the TIREFIT sticker must be affixed to the
instrument cluster in the driver's field of
vision. 284
Flat tire
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necessary for you to disconnect the battery
yourself, make sure that:
R
you switch off
the engine and remove the
SmartKey. Check that all the indicator
lamps in the instrument cluster are off.
Otherwise, electronic components, such
as the alternator, may be damaged.
R you first remove the negative terminal
clamp and then the positive terminal
clamp. Never swap the terminal clamps.
Otherwise, the vehicle's electronic
system may be damaged.
R on vehicles with automatic transmission,
the transmission is locked in position P
after disconnecting the battery. The
vehicle is secured against rolling away.
You can then no longer move the vehicle.
The battery and the cover of the positive
terminal clamp must be installed securely
during operation.
Comply with safety precautions and take
protective measures when handling
batteries. WARNING
Fire, open flames and smoking are
prohibited when handling the
battery. Avoid creating sparks.
Battery acid is caustic. Avoid
contact with the skin, eyes or
clothing.
Wear suitable protective clothing,
in particular gloves, an apron and
a face mask.
Immediately rinse acid splashes
off with clean water. Consult a
doctor if necessary.
Wear eye protection. Keep children away.
Observe this Operator's Manual.
For safety reasons, Mercedes-Benz
recommends that you only use batteries
which have been tested and approved for
your vehicle by Mercedes-Benz. These
batteries provide increased impact
protection to prevent

vehicle occupants from
suffering acid burns should the battery be
damaged in the event of an accident.
In order for the battery to achieve the
maximum possible service life, it must always
be sufficiently charged.
Like other batteries, the vehicle battery may
discharge over time if you do not use the
vehicle. In this case, have the battery
disconnected at a qualified specialist
workshop. You can also charge the battery
with a charger recommended by Mercedes-
Benz. Contact a qualified specialist workshop
for further information.
Have the battery charge level checked more
frequently if you use the vehicle mainly for
short trips or if you leave it standing idle for
a lengthy period. Consult a qualified specialist
workshop if you wish to leave your vehicle
parked for a long period of time.
Only replace a battery with a battery that has
been recommended by Mercedes-Benz.
i Remove the SmartKey if you park the
vehicle and do not require any electrical
consumers. The vehicle will then use very
little energy, thus conserving battery
power. Battery (vehicle)
287
Breakdown assistance Z
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i
If the power supply has been interrupted,
e.g. if you reconnect the battery, you will
have to:
R set the clock (audio system/COMAND,
see the
separate operating instructions).
R reset the function for folding the exterior
mirrors in/out automatically, by folding
the mirrors out once ( Y page 93).Charging the battery
G
WARNING
During charging and jump-starting, explosive
gases can escape

from the battery. There is a
risk of an explosion.
Particularly avoid fire, open flames, creating
sparks and smoking. Ensure there is sufficient
ventilation while charging and jump-starting.
Do not lean over a battery. G
WARNING
Battery acid is caustic. There is a risk of injury.
Avoid contact with

the skin, eyes or clothing.
Do not inhale any battery gases. Do not lean
over the battery. Keep children away from
batteries. Wash battery acid immediately with
water and seek medical attention. G
WARNING
A discharged battery can freeze at
temperatures below freezing point. When
jump-starting the vehicle or charging the
battery, gases can escape from the battery.
There is a risk of an explosion.
Allow the frozen battery to thaw out before
charging it or jump-starting.
! Only use battery chargers with a
maximum charging voltage of 14.8 V.
! Only charge the battery using the jump-
starting connection point.
The jump-starting connection point is in the
engine compartment (Y

page 289). X
Open the hood (Y page 266).
X Connect the battery charger to the positive
terminal and ground point in the same
order as when connecting the donor
battery in the jump-starting procedure
(Y page 289).
If, at low temperatures, the indicator lamps/
warning lamps in the instrument cluster do
not light up, it is highly likely that the
discharged battery has frozen. In this case
you may neither jump-start the vehicle nor
charge the battery. The service life of a
thawed-out battery may be shorter. The
starting characteristics can be impaired,
particularly at low temperatures. Have the
thawed-out battery checked at a qualified
specialist workshop.
Only charge the installed battery with a
battery charger which has been tested and
approved by Mercedes-Benz. An accessory
battery charge unit specially adapted for
Mercedes-Benz vehicles and tested and
approved by Mercedes-Benz is available. It
permits the charging of the battery in its
installed position. Contact an authorized
Mercedes-Benz Center for further
information and availability.

Read the battery
charger's operating instructions before
charging the battery. 288
Battery (vehicle)
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Jump-starting
For the jump-starting
procedure, use only the jump-starting connection point, consisting of a
positive terminal and an earth point, in the engine compartment. G
WARNING
Battery acid is caustic. There is a risk of injury.
Avoid contact with the skin, eyes or clothing. Do not inhale any battery gases. Do not lean over
the battery. Keep children away from batteries. Wash battery acid immediately with water and
seek medical attention. G
WARNING
During charging and jump-starting, explosive gases can escape from the battery. There is a risk
of an explosion.
Particularly avoid fire, open flames, creating sparks and smoking. Ensure there is sufficient
ventilation while charging and jump-starting. Do not lean over a battery. G
WARNING
During the charging process, a battery produces hydrogen gas. If a short circuit occurs or sparks
are created, the hydrogen gas can ignite. There is a risk of an explosion.
R Make sure that the positive terminal of a connected battery does not come into contact with
vehicle parts.
R Never place metal objects or tools on a battery.
R It is important

that you observe the described order of the battery terminals when connecting
and disconnecting a battery.
R When jump-starting, make sure that the battery poles with identical polarity are connected.
R It is particularly important to observe the described order when connecting and disconnecting
the jumper cables.
R Never connect or disconnect the battery terminals while the engine is running. G
WARNING
A discharged battery can freeze at temperatures below freezing point. When jump-starting the
vehicle or charging

the battery, gases can escape from the battery. There is a risk of an explosion.
Allow the frozen battery to thaw out before charging it or jump-starting. G
WARNING
Non-combusted fuel can collect in the exhaust system and ignite. There is a risk of fire. Avoid
repeated and lengthy starting attempts.
! Avoid repeated and

lengthy starting attempts. Otherwise, the catalytic converter could be
damaged by the non-combusted fuel.
If, at low temperatures, the indicator lamps/warning lamps in the instrument cluster do not
light up, it is highly likely that the discharged battery has frozen. In this case you may neither
jump-start the vehicle nor charge the battery. The service life of a thawed-out battery may be Jump-starting
289
Breakdown assistance Z
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