ECU MERCEDES-BENZ B-CLASS HATCHBACK 2014 Repair Manual

Display messages
Possible causes/consequences and
M
MSolutions &
inoperative Bat‐ inoperative Bat‐
tery weak tery weak The on-board voltage is too low The auxiliary heating has switched
itself off or cannot be switched on (Y page 150).
X Drive for a considerable distance.
The battery charges. The auxiliary heating is operational again as
soon as the on-board electrical system voltage is sufficient. &
inoperative inoperative
Refuel
Refuel
vehicle
vehicle There is too little fuel in the fuel tank. The auxiliary heating cannot
be switched on (Y page 150).
X Refuel at the nearest filling station. &
inoperative See inoperative See
Owner's Manual Owner's Manual The auxiliary heating is temporarily malfunctioning or faulty.
X When the vehicle is on a level surface and the engine has cooled
down, make up to four attempts to switch on the auxiliary heat- ing, waiting several minutes between each attempt
(Y page 150).
X If the auxiliary heating does not switch on, consult a qualified
specialist workshop. Ð
Power Power
steering
steering mal‐
mal‐
function See Own‐
function See Own‐
er's Manual er's Manual The power steering assistance is faulty.
A warning tone also sounds.
G WARNING
You will need to use more force to steer.
There is a risk of an accident. X Check whether you are able to apply the extra force required.
X If you are able to steer safely: carefully drive on to a qualified
specialist workshop.
X If you are unable to steer safely: do not drive on. Contact the
nearest qualified specialist workshop. Ð
Steering malfunc‐ Steering malfunc‐
tion See Owner's tion See Owner's
Manual Manual The electric steering lock is malfunctioning.
G WARNING
The steering may be locked by the electric steering lock.
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.
X Secure the vehicle against rolling away (Y page 181).
X Do not drive on and consult the nearest qualified specialist
workshop. 282
Display
messagesOn-board computer and displays

Display messages
Possible causes/consequences and
M
MSolutions Â
Key not detected Key not detected
(red display message) The key is not in the vehicle.
A warning tone also sounds.
If the engine is switched off, you can no longer lock the vehicle
centrally or start the engine.
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 181).
X Locate the key. Because there is interference from a strong source of radio waves,
the key is not detected whilst the engine is running.
A warning tone also sounds.
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 181).
X Insert the key into the ignition lock and bring into key mode. Â
Key not detected Key not detected
(white display mes-
sage) The key is currently undetected.
X Change the location of the key in the vehicle.
If the key still cannot be detected: X Operate the vehicle with the key in the ignition lock if necessary. Â
Remove starting Remove starting
button, then button, then
insert key insert key The key is continually undetected.
KEYLESS-GO is temporarily malfunctioning or is defective. A warn-
ing tone also sounds.
X Insert the key into the ignition lock and turn it to the desired
position.
X Visit a qualified specialist workshop. Warning and indicator lamps in the instrument cluster
General notes
Some systems perform a self test when the ignition is switched on. Some warning and indicator
lamps may temporarily switch on or flash during the test. This behaviour is nothing to be
concerned about.
The warning and indicator lamps will alert you to a malfunction if they switch on or flash after the engine is started or while driving. 284
Wa
rning and indi cator lamps in the instrument clusterOn-board computer and displays

Safety
Seat belts Problem
Possible causes/consequences and
M
MSolutions ü
Only for certain coun-
tries: the red seat belt
warning lamp lights up
for 6 seconds after the
engine starts.
The seat belt warning lamp reminds the driver and front passenger
to fasten their seat belts.
X Fasten your seat belt (Y page 44).ü
Only for certain coun-
tries: the red seat belt
warning lamp lights up
after the engine starts.
In addition, a warning
tone sounds for up to
6 seconds.
The driver's seat belt is not fastened.
X Fasten your seat belt (Y page 44).
The warning tone ceases. ü
The red seat belt warn-
ing lamp lights up after
the engine starts, as
soon as the driver's or
the front-passenger
door is closed.
The driver or passenger has not fastened their seat belt.
X Fasten your seat belt (Y page 44).
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 warn-
ing lamp flashes and an
intermittent audible
warning sounds. The driver or passenger has not fastened their seat belt. At the
same time, you are driving faster than 25 km/h or have briefly
driven faster than 25 km/h.
X Fasten your seat belt (Y page 44).
The warning lamp goes out and the intermittent warning tone
ceases. There are objects on the front-passenger seat. At the same time,
you are driving faster than 25 km/h or have briefly driven faster
than 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. Wa
rning and indi cator lamps in the instrument cluster
285On-board computer and displays Z

Safety systems
Problem
Possible causes/consequences and
M
MSolutions J
The red brake system
warning lamp is lit while
the engine is running. A
warning tone also
sounds. G
WARNING
The brake boosting effect is malfunctioning and the braking char- acteristics may be affected.
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 181).
X Consult a qualified specialist workshop.
X Observe the additional display messages in the multifunction
display. J
The red brake system
warning lamp is lit while
the engine is running. A
warning tone also
sounds. There is insufficient brake fluid in the brake fluid reservoir.
G WARNING
Braking efficiency 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 181).
X Do not top up the brake fluid. Topping up will not rectify the fault.
X Consult a qualified specialist workshop.
X Observe the additional display messages in the multifunction
display. 286
Warning and indicator lamps in the instrument clusterOn-board computer and displays

Engine
Problem
Possible causes/consequences and
M
MSolutions ;
The yellow engine diag-
nostics warning lamp
lights up while the
engine is running. There may be a fault, for example:
R in the engine management
R in the fuel injection system
R in the exhaust system
R in the ignition system (for vehicles with petrol engines)
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. Vehicles with a diesel engine: the fuel tank has been run dry
(Y
page 180).
X Start the engine three to four times after refuelling.
If the yellow engine diagnostics warning lamp goes out, emer-
gency running mode is cancelled. The vehicle need not be
checked. æ
The yellow reserve fuel
warning lamp is on
while the engine is run-
ning.
The fuel level has dropped into the reserve range.
Operation of the auxiliary heating is deactivated if the fuel level
drops into the reserve range.
X Refuel at the nearest filling station. ?
The red coolant warn-
ing lamp lights up while
the engine is running
and the coolant tem-
perature gauge is at the start of the scale. The temperature sensor for the coolant temperature gauge is
faulty.
The coolant temperature is no longer being monitored. There is a risk of engine damage if the coolant temperature is too high.
X Stop the vehicle immediately, paying attention to road and traf-
fic conditions, and switch off the engine. Do not continue driving
under any circumstances.
X Secure the vehicle against rolling away (Y page 181).
X Consult a qualified specialist workshop. Warning and indicator lamps in the instrument cluster
293On-board computer and displays Z

Problem
Possible causes/consequences and
M
MSolutions ?
The red coolant warn-
ing lamp comes on
while the engine is run-
ning.
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 malfunc-
tioning.
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 Stop the vehicle immediately, paying attention to road and traf-
fic conditions, and switch off the engine.
X Secure the vehicle against rolling away (Y page 181).
X Leave the vehicle and keep a safe distance from the vehicle until
the engine has cooled down.
X Check the coolant level and top up the coolant, observing the
warning notes (Y page 322).
X If you have to top up the coolant frequently, have the engine
cooling system checked.
X Make sure that the air supply to the engine radiator is not
blocked, e.g. by frozen slush.
X Do not start the engine again until the coolant temperature is
below 120 †. The engine may otherwise be damaged.
X Drive to the nearest qualified specialist workshop.
X Avoid putting the engine under heavy load as you do so, e.g.
driving in mountainous terrain and stop-start traffic. ?
The red coolant warn-
ing lamp comes on
while the engine is run-
ning. A warning tone
also sounds.
The coolant temperature has exceeded 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.
Never drive with an overheated engine. Driving when your engine is overheated can cause some fluids which may have leaked into
the engine compartment to catch fire.
In addition, steam from an overheated engine can cause serious
burns, which can occur just by opening the bonnet.
There is a risk of injury.
X Observe the additional display messages in the multifunction
display.
X Stop the vehicle immediately, paying attention to road and traf-
fic conditions, and switch off the engine.
X Secure the vehicle against rolling away (Y page 181).294
Warning and indicator lamps in the instrument clusterOn-board computer and displays

Tyres
Problem
Possible causes/consequences and
M
MSolutions h
The yellow tyre pres-
sure monitor warning
lamp (pressure loss/
malfunction) is lit.
The tyre pressure monitor has detected a loss of pressure in at
least one of the tyres.
G WARNING
Underinflated tyres pose the following risks:
R the tyres may burst, especially as the load and vehicle speed
increase
R the tyres may wear excessively and/or unevenly, which may
greatly impair tyre traction
R the driving characteristics, as well as steering and braking, may
be greatly impaired
There is a risk of an accident.
X Stop the vehicle without making any sudden steering or braking
manoeuvres. Pay attention to the traffic conditions as you do so.
X Secure the vehicle against rolling away (Y page 181).
X Observe the additional display messages in the multifunction
display.
X Check the tyres and, if necessary, follow the instructions for a
flat tyre (Y page 334).
X Check the tyre pressure (Y page 358).
X If necessary, correct the tyre pressure. h
The yellow tyre pres-
sure monitor warning
lamp (pressure loss/
malfunction) flashes for
approximately one
minute and then
remains lit. The tyre pressure monitor is faulty.
G WARNING
The system is possibly unable to detect or register low tyre pres-
sure.
There is a risk of an accident. X Observe the additional display messages in the multifunction
display.
X Visit a qualified specialist workshop. 296
Warning and indicator lamps in the instrument clusterOn-board computer and displays

Useful information
i This Owner's Manual describes all mod-
els, series and optional equipment for your
vehicle that were available at the time of
going to press. National variations are pos- sible. Note that your vehicle may not be
equipped with all of the functions descri-
bed. This is also the case for systems and
functions relevant to safety.
i Read the information on qualified special-
ist 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, especially when braking or abruptly changing directions.
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, particu-
larly 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 tail-
gate. Never drive with the tailgate open. G
WARNING
The exhaust tail pipe and tail pipe trim can
become very hot. If you come into contact
with these parts of the vehicle, you could burn
yourself. There is a risk of injury.
Always be particularly careful around the
exhaust tail pipe and the tail pipe trim. Allow
these components to cool down before touch-
ing them. The handling characteristics of a laden vehi-
cle 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 permissible axle
loads for the vehicle (including occupants).
R the luggage compartment is the preferred
place to carry objects.
R position heavy loads as far forwards as pos-
sible and as low down in the load compart-ment 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 lashing eyelets and the luggage
nets to transport loads and luggage.
R only use lashing eyelets and fastening com-
ponents that are suitable for the weight and size of the load.
R hook in the safety net when loading.
R the maximum load capacity of the stowage
well under the luggage compartment floor
is 25 kg.
R secure the load with sufficiently strong and
wear-resistant lashing material. pad sharp
edges for protection.
! Do not position the load on one part of the
folding luggage compartment floor only.
The maximum load capacity of the folding
luggage compartment floor is 100 kg.
Spread the weight evenly to avoid damag-
ing the luggage compartment floor. Place a
solid board under the load if necessary.
Please note that the load on the luggage
compartment floor will be increased when
the load is lashed down. 298
Loading guidelinesStowing and features

Stowage areas
Stowage compartments
Important safety notes G
WARNING
If you do not correctly store objects in the
vehicle interior, they can slip or be flung
around, thus striking vehicle occupants.
There is a risk of injury, especially when brak- ing or abruptly changing directions.
R Always store objects so that they cannot be
flung around in these or in similar situa-
tions.
R Always make sure that objects do not pro-
trude from stowage compartments, lug-
gage nets or stowage nets.
R Close lockable stowage compartments
while driving.
R Stow and secure objects that are heavy,
hard, pointy, sharp-edged, fragile or too
large in the luggage compartment.
Observe the loading guidelines (Y page 298).
Front stowage compartments Glove compartment
X
To open: pull handle :and open glove
compartment flap ;.
X To close: fold glove compartment flap ;
upwards until it engages.
There is a pen holder at the top of the glove
compartment flap. Spectacles compartment
X
To open: press marking :.
Make sure that the spectacles compartment
is always closed while the vehicle is in motion.
Stowage compartment in the front centreconsole Illustration: vehicles with DIRECT SELECT
lever
X To open: press the marking on cover :.
i Depending on the vehicle's equipment,
there may be an ashtray in the centre con-
sole instead of the stowage compartment. Stowage areas
299Stowing and features Z

Stowage compartment in front of the arm-
rest (vehicles with automatic transmis-
sion) Vehicles with DIRECT SELECT lever
X To open: press the marking on cover :.
i You can remove the non-slip mat and the
insert for cleaning. When removing the
insert you will have to overcome some
slight resistance.
Stowage compartment/telephone com-
partment under the armrest X
To open: on vehicles with moveable armr-
ests, make sure that the armrest is in the
rearmost position.
X Press button :and fold the armrest up.
Depending on the vehicle equipment, the
armrest can be moved backwards or forwards
in a longitudinal direction.
Depending on the vehicle's equipment, the
following may be in the stowage space:
R a multimedia connector unit with an SD
card slot and 2 USB ports, e.g. for use with an iPod
®
, iPhone ®
or MP3 player; see the
separate operating instructions
R a mobile phone bracket (Y page 314)
Stowage compartment under the driver's and front-passenger seat G
WARNING
If you exceed the maximum permitted load of the stowage compartment, the cover is
unable to restrain the objects. Objects may be
thrown out of the stowage compartment and
hit vehicle occupants as a result. There is a
risk of injury, particularly in the event of sud-
den braking or a sudden change in direction.
Always observe the maximum load of the
stowage compartment. Stow and secure
heavy objects in the luggage compartment.
The maximum permissible load of the stow-
age compartment is 1.2 kg. X
To open: pull handle :up and fold
cover ;forwards.
On vehicles with a fire extinguisher instead of
a stowage compartment, the fire extinguisher
is installed under the driver's seat. 300
Stowage areasStowing and features