2012 MERCEDES-BENZ B-CLASS key battery

Problems with the engine
Problem Possible causes/consequences and
M SolutionsThe engine does not
start. The HOLD function or DISTRONIC PLUS is activated.
X
Deactivate the HOLD function (Y page 167) or DISTRONIC
PLUS (Y page 159).
X Try to start the engine again. The engine does not
start.
The starter
motor
can be heard. R
There is a malfunction in the engine electronics.
R There is a malfunction in the fuel supply.
X Turn the SmartKey back to position 0
in the

ignition lock before
attempting to start the engine again.
X Try to start the engine again (Y page 135). Avoid excessively
long and frequent

attempts to start the engine as these will drain
the battery.
If the engine does not start after several attempts:
X Consult a qualified specialist workshop. The engine does not
start. You cannot hear
the starter motor. The on-board voltage is too low because the battery is too weak
or discharged.
X
Jump-start the vehicle (Y page 289).
If the engine does not start despite attempts to jump-start it:
X Consult a qualified specialist workshop, e.g. an authorized
Mercedes-Benz Center. The starter motor was exposed to a thermal load that was too high.
X
Allow the starter motor to cool down for approximately two
minutes.
X Try to start the engine again.
If the engine still does not start:
X Consult a qualified specialist workshop. Driving
139Driving and parking Z
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Problems with fuel and the fuel tank
Problem Possible causes/consequences and
M SolutionsFuel is leaking from the
vehicle. The fuel line or the fuel tank is faulty.
G WARNING
Risk of explosion or fire.
X Turn the SmartKey to position 0
in the
ignition lock immediately
and remove it (Y page 135).
X Do not restart the engine under any circumstances.
X Consult a qualified specialist workshop. The fuel filler flap
cannot be opened. The fuel filler flap is not unlocked.
or
The SmartKey battery is discharged.
X
Unlock the vehicle (Y page 68).
or
X Unlock the vehicle using the mechanical key ( Y page 69).The fuel filler flap is unlocked, but the opening mechanism is
jammed.
X
Consult a qualified specialist workshop. Parking
Important safety notes
G
WARNING
If flammable materials such as leaves, grass
or twigs are

exposed to prolonged contact to
parts of the exhaust system that heat up, they
could ignite. There is a risk of fire.
Park the vehicle so that no flammable
materials come into contact with parts of the
vehicle which are hot. Take particular care not
to park on dry grassland or harvested grain
fields. G
WARNING
If you leave children unsupervised in the
vehicle, they could set it in motion by, for
example:
R releasing the parking brake
R shifting the automatic transmission out of
the parking position P
R starting the engine.
They could also operate the vehicle's
equipment. There is

a risk of an accident and
injury.
When leaving the vehicle, always take the
SmartKey with you and lock the vehicle. Never
leave children unsupervised in the vehicle.
! Always secure the vehicle correctly
against rolling away. Otherwise, the vehicle
or its drivetrain could be damaged. Parking
149
Driving and parking Z
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Display messages Possible causes/consequences and
M SolutionsThe yellow
! warning lamp lights up. If you manually apply or
release the electric parking brake, the red F (USA
only)/! (Canada only) indicator lamp flashes.
The electric parking brake is malfunctioning. It is not possible to
apply the electric parking brake manually.
X Shift the transmission to P.
X Visit a qualified specialist workshop. F(USA
only)!(Canada
only)
Parking Brake
Inoperative The yellow
! warning lamp lights up. The red F (USA
only)/! (Canada only) indicator lamp flashes for about ten
seconds after the electric parking brake has been applied or
released. It then goes out or remains lit.
The electric parking brake is malfunctioning, e.g. because of
overvoltage or undervoltage.
X Remove the cause for the overvoltage or undervoltage, e.g. by
charging the battery or restarting the engine.
X Engage or release the electric parking brake.
If it remains impossible to apply or release the electric parking
brake:
X Switch off the ignition and turn it back on.
X Engage or release the electric parking brake.
If the electric parking brake still cannot be released:
X Consult a qualified specialist workshop. The display message is only shown while the vehicle is in motion.
The yellow
! warning lamp lights up and the red F (USA
only)/ ! (Canada only) indicator lamp flashes.
It is not possible to apply the electric parking brake manually.
X Shift the transmission to P.
X Visit a qualified specialist workshop. F(USA
only)!(Canada
only)
Turn On the
Ignition to
Release the
Parking Brake The red
F (USA
only)/ ! (Canada only) indicator lamp lights
up.
You attempted to release the electric parking brake while the
ignition was switched off.
X Turn the SmartKey to position 1 in the ignition lock.206
Display messages
On-board computer and displays
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i
If you remove the ashtray insert, you can
use the resulting compartment for
stowage.
Rear-compartment ashtray X
To open: pull cover = out by its top edge.
X To remove: pull insert ; by recess : in
the direction of arrow ? until it audibly
releases.
X Lift insert ; up and out.
X To install the insert: place
insert ;
from
above into the holder and press down until
it engages. Cigarette lighter
G
WARNING
You can burn yourself if you touch the hot
heating element or

the socket of the cigarette
lighter.
In addition, flammable materials can ignite if:
R the hot cigarette lighter falls
R a child holds the hot cigarette lighter to
objects, for example
There is a risk of fire and injury.
Always hold the cigarette lighter by the knob.
Always make sure that the cigarette lighter is
out of reach of children. Never leave children
unsupervised in the vehicle.
Your attention must always be focused on the
traffic conditions. Only use the cigarette lighter when road and traffic conditions
permit.
Example: vehicles with a cover over the stowage
compartment
X
Turn the SmartKey to position 2 in the
ignition lock (Y page 135).
X To open: push the lower section of
cover :.
The stowage compartment opens.
X Press in cigarette lighter ;.
Cigarette lighter ; will pop out
automatically when the heating element is
red-hot. 12 V sockets
Points to observe before use X
Turn the SmartKey to position 1 in the
ignition lock (Y page 135).
The sockets can be used for accessories with
a maximum draw of 180 W (15 A).
Accessories include such items as lamps or
chargers for mobile phones.
If you use the sockets for long periods when
the engine is switched off, the battery may
discharge.
i An emergency cut-out ensures that the
on-board voltage does not drop too low. If
the on-board voltage is too low, the power
to the sockets is automatically cut. This
ensures that there is sufficient power to
start the engine. 250
Features
Stowage and features
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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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shorter. The starting characteristics can be impaired, particularly at low temperatures. Have
the thawed-out battery checked at a qualified specialist workshop.
Do not
start
the vehicle using a rapid charging device. If your vehicle's battery is discharged,
the engine can be jump-started from another vehicle or from a second battery using jumper
cables. Observe the following points:
R The battery is not accessible in all vehicles. If the other vehicle's battery is not accessible,
jump-start the vehicle using a second battery or a jump-starting device.
R You may only jump-start the vehicle when the engine and exhaust system are cold.
R Do not start the engine if the battery is frozen. Let the battery thaw first.
R Jump-starting may only be performed from batteries with a nominal voltage of 12 V.
R Only use jumper cables which have a sufficient cross-section and insulated terminal clamps.
R If the battery is fully discharged, leave the battery that is being used to jump-start connected
for a few minutes before attempting to start. This charges the battery slightly.
R Make sure that the two vehicles do not touch.
Make sure that:
R the jumper cables are not damaged.
R bare parts of the terminal clamp do not come into contact with other metal parts while the
jumper cables are connected to the battery.
R the jumper cables cannot come into contact with parts which can move when the engine
is running, such as the V-belt pulley or the fan.
X Secure the vehicle by applying the electric parking brake.
X Shift the transmission to position P.
X Turn the SmartKey to position 0 in the ignition lock and remove it.
X Switch off all electrical consumers (e.g. radio, blower, etc.).
X Open the hood (Y page 266).290
Jump-starting
Breakdown assistance
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!
Only secure the
tow rope or tow bar at the
towing eyes. Otherwise, the vehicle could
be damaged.
! Do not use the towing eyes for recovery
purposes as this could damage the vehicle.
If in doubt, recover the vehicle with a crane.
! When towing, pull away slowly and
smoothly. If the tractive power is too high,
the vehicles could be damaged.
! The vehicle can be towed a maximum of
30 miles (50km). The towing speed of
30 mph (50km/h) must not be exceeded.
If the vehicle has to be towed more than
30 miles (50km), the front axle must be
raised or the entire vehicle raised and
transported.
! Do not tow with sling-type equipment.
This could damage the vehicle.
! Vehicles with automatic transmission
must not be started by tow-starting. This
could otherwise damage the transmission.
It is better to have the vehicle transported
than to have it towed.
When towing a vehicle, the transmission must
be in position N.
The battery must be connected and charged.
Otherwise, you:
R cannot turn the SmartKey to position 2 in
the ignition lock
R cannot shift the transmission to position
N.
i Deactivate the automatic locking feature
(Y page 198). You could otherwise be
locked out when pushing or towing the
vehicle. Installing/removing the towing eye
Installing the towing eye X
Remove the towing eye from the stowage
space.
The towing eye is beneath the cargo
compartment floor with

the vehicle tool kit
(Y page 280).
Vehicles with the TIREFIT kit: the towing
eye is beneath the tire inflation
compressor.
X Press the mark on cover : inwards in the
direction of the arrow.
X Take cover : off the opening.
X Screw in and tighten the towing eye
clockwise to the stop.
Removing the towing eye X
Unscrew and remove the towing eye.
X Attach cover : to the bumper and press
until it engages.
X Place the towing eye in the stowage well
beneath the cargo compartment floor
(Y page 280) in the cargo compartment.
X Vehicles with the TIREFIT kit: put back the
tire inflation compressor.292
Towing and tow-starting
Breakdown assistance
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