2012 MERCEDES-BENZ B-CLASS ECU

Vehicle
Display messages Possible causes/consequences and
M SolutionsShift to 'P' or 'N'
to Start Engine You have attempted to start the engine with the transmission in
position R or D.
X
Shift the transmission to position P or N.Auxiliary Battery
Malfunction The auxiliary battery for the automatic transmission is no longer
being charged.
X
Visit a qualified specialist workshop at the next opportunity.
X Until then, set the automatic transmission to position P before
you switch off the engine.
X Before leaving the vehicle, apply the electric parking brake. Depress Brake to
Start Engine You have attempted to start the engine with the transmission in
position N without depressing the brake pedal.
X
Depress the brake pedal. To Deselect P or N,
Depress Brake and
Start Engine You have attempted to shift the transmission to position
R or D
without starting the engine.
X Start the engine.
X Depress the brake pedal.
i It is only possible to shift the transmission from position P to
the desired position if you depress the brake pedal. Only then
can the parking lock be deactivated. If you do not depress the
brake pedal, you can move the DIRECT SELECT lever but the
parking lock remains engaged.
i At transmission fluid temperatures below Ò4 ‡ (Ò20 †) you
can only shift out of position P into another transmission
position when the engine is running. Apply Brake to
Shift from 'P' You have attempted to move the transmission selector lever to
position R, N or D without depressing the brake pedal.
X
Depress the brake pedal. Transmission Not
in P
Risk of Vehicle
Rolling Away The driver's door is open and the transmission is in position
R, N
or D.
A warning tone also sounds.
X Shift the transmission to position P.
X Secure the vehicle against rolling away ( Y page 149).220
Display messagesOn-board computer and displays
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Display messages Possible causes/consequences and
M SolutionsService Required
Do Not Shift Gears
Visit Dealer You cannot change the transmission position due to a malfunction.
A warning tone also sounds.
If transmission position
D is selected:
X Drive to a qualified specialist workshop without shifting the
transmission from position D.
If transmission position R, N or P is selected:
X Notify a qualified specialist workshop or breakdown service. Only Shift
to 'P' when
Vehicle is
Stationary The vehicle is moving.
X
Pull over and stop the vehicle safely as soon as possible, paying
attention to road and traffic conditions.
X Shift the transmission to position P.Reversing Not
Possible Service
Required The automatic transmission is malfunctioning. You cannot back
up.
X
Visit a qualified specialist workshop. Transmission
Malfunction The automatic transmission is malfunctioning.
X
Visit a qualified specialist workshop. Transmission
Malfunction Stop The automatic transmission is malfunctioning.
X
Pull over and stop the vehicle safely as soon as possible, paying
attention to road and traffic conditions.
X Secure the vehicle against rolling away ( Y page 149).
X Consult a qualified specialist workshop. Stop Vehicle Shift
to P Leave Engine
Running The automatic transmission has overheated.
X
Drive on carefully.
The automatic transmission
is available again when the display
message goes out.
If the display message continues to be displayed:
X Pull over and stop the vehicle safely as soon as possible, paying
attention to road and traffic conditions.
X Secure the vehicle against rolling away ( Y page 149).
X Wait until the automatic transmission has cooled down and the
display message has disappeared. Display messages
221
On-board computer and displays Z
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Warning and indicator lamps in the instrument cluster
Seat belts
Problem Possible causes/consequences and
M Solutionsü
After starting the
engine, the red seat
belt warning
lamp
lights
up for six seconds. The seat belt warning lamp reminds the driver and front passenger
to fasten their seat belts.
X
Fasten your seat belt ( Y page 45).ü
After starting the
engine, the red seat
belt warning
lamp

lights
up. In addition, a
warning tone sounds
for up to six seconds. The driver's seat belt is not fastened.
X
Fasten your seat belt ( Y page 45).
The warning tone ceases. ü
The red seat belt
warning lamp lights up
after the engine starts,
as soon as the driver's
or the front-passenger
door is closed.
The driver or front passenger has not fastened their seat belt.
X
Fasten your seat belt ( Y page 45).
The warning lamp goes out. There are objects on the front-passenger seat.
X
Remove the objects from the front-passenger seat and stow
them in a secure place.
The warning lamp goes out. ü
The red seat belt
warning lamp flashes
and an intermittent
audible warning
sounds.
The driver or front passenger has not fastened their seat belt. In
addition,
you are

driving faster than 15 mph (25 km/h) or you have
briefly driven faster than 15 mph (25 km/h).
X Fasten your seat belt ( Y page 45).
The warning lamp goes out and the intermittent warning tone
ceases. There are objects on the front-passenger seat. In addition, you are
driving faster than 15 mph (25 km/h
) or you have briefly driven
faster than 15 mph (25 km/h ).
X Remove the objects from the front-passenger seat and stow
them in a secure place.
The warning lamp goes out and the intermittent warning tone
ceases.224
Warning and indicator lamps in the instrument cluster
On-board computer and displays
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Safety systems
Problem Possible causes/consequences and
M Solutions$ (USA only)
J (Canada only)
The red brake system
warning
lamp comes
on
while the engine is
running. A warning tone
also sounds. There is not enough brake fluid in the brake fluid reservoir.
G WARNING
The braking effect may be impaired.
There is a risk of an accident.
X Pull over and stop the vehicle safely as soon as possible, 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 Do not add brake fluid. Adding more will not remedy the
malfunction.
X Consult a qualified specialist workshop.
X Observe the additional display messages in the multifunction
display. !
The yellow
ABS

warning
lamp is lit while the
engine is running. ABS (Anti-lock Braking System) is deactivated due to a
malfunction. BAS (Brake Assist), COLLISION PREVENTION
ASSIST, ESP
®
(Electronic Stability Program), the HOLD function
and hill start assist are therefore also deactivated, for example.
ATTENTION ASSIST is deactivated.
G WARNING
The brake system continues to function normally, but without the
functions listed above. The wheels could therefore lock if you
brake hard, for example.
The steerability and braking characteristics may be severely
affected. The braking distance in an emergency braking situation
can increase.
If ESP ®
is not

operational, ESP ®
is unable to stabilize the vehicle.
There is an increased risk of skidding and an accident.
X Observe the additional display messages in the multifunction
display.
X Drive on carefully.
X Visit a qualified specialist workshop.
If the ABS control unit is faulty, there is also a possibility that other
systems, such as the navigation system or the automatic
transmission, will not be available. Warning and indicator lamps in the instrument cluster
225
On-board computer and displays Z
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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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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 Read the information on qualified
specialist workshops: ( Y page 24).Loading guidelines
G
WARNING
If objects, luggage or loads are not secured or
not secured sufficiently, they could slip, tip
over or be

flung around and thereby hit vehicle
occupants. There is a risk of injury,
particularly in the event of sudden braking or
a sudden change in direction.
Always store objects so that they cannot be
flung around. Secure objects, luggage or
loads against slipping or tipping before the
journey. G
WARNING
Combustion engines emit poisonous exhaust
gases such as

carbon monoxide. If the tailgate
is open when the engine is running,
particularly if the vehicle is moving, exhaust
fumes could enter the passenger
compartment. There is a risk of poisoning.
Turn off the engine before opening the
tailgate. Never drive with the tailgate open.
The handling characteristics of a laden
vehicle are dependent on the distribution of
the load within the vehicle. For this reason,
you should observe the following notes when
transporting a load:
R Never exceed the maximum permissible
gross vehicle weight or the gross axle weight rating of the vehicle (including
occupants). The
values

are specified on the
vehicle identification plate on the B-pillar of
the driver's door.
R The cargo compartment is the preferred
place to carry objects.
R Position heavy loads as far forwards as
possible and as low down in the cargo
compartment as possible.
R The load must not protrude above the
upper edge of the seat backrests.
R Always place the load against the rear or
front seat backrests. Make sure that the
seat backrests are securely locked into
place.
R Always place the load behind unoccupied
seats if possible.
R Use the cargo tie down rings and the parcel
nets to transport loads and luggage.
R Use cargo tie-down rings and fastening
materials appropriate for the weight and
size of the load.
R Hook in the cargo net when loading.
R The maximum load capacity of the stowage
well under the cargo compartment floor is
55 lbs (25 kg).
R Secure the load with sufficiently strong and
wear-resistant tie-downs. pad sharp edges
for protection.
! Do not position the load on one part of the
folding cargo compartment floor only. The
maximum load capacity of the folding cargo
compartment floor is 220 lbs (100 kg).
Distribute the weight evenly to avoid
damaging the cargo compartment floor.
Place a solid board under the load if
necessary. Please note that the load on the
cargo compartment floor will be increased
when the load is lashed down. 236
Loading guidelines
Stowage and features
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Stowage areas
Stowage space
Important safety notes G
WARNING
If objects in the passenger compartment are
stowed incorrectly, they can slide or be
thrown around and hit vehicle occupants.
There is a risk of injury, particularly in the
event of sudden braking or a sudden change
in direction.
R Always stow objects
so that they cannot be
thrown around in such situations.
R Always make sure that objects do not
protrude from stowage spaces, parcel nets
or stowage nets.
R Close the lockable stowage spaces while
driving.
R Stow and secure objects that are heavy,
hard, pointy, sharp-edged, fragile or too
large in the cargo compartment.
Observe the loading guidelines (Y page 236).
Stowage compartments in the front Glove box
X
To open: pull handle :
and open glove box
flap ;.
X To close: fold glove box flap ; upwards
until it engages.
i There is a pen holder at the top of the
glove box flap. Eyeglasses compartment
X
To open: press marking :.
Make sure that the eyeglasses compartment
is always closed

while the vehicle is in motion.
Stowage compartment in the center
console X
To open: press the marking on cover :.
i Depending on the vehicle's equipment,
there is an open instead of a closed
stowage compartment or

an ashtray in the
center console. Stowage areas
237
Stowage and features Z
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