2012 MERCEDES-BENZ A CLASS radiator

Problem Possible causes/consequences and
M SolutionsVehicles with a petrol
engine:
The engine is not run-
ning smoothly and is
misfiring. There is a malfunction in the engine electronics or in a mechanical
component of the engine management system.
X
Only depress the accelerator pedal slightly.
Otherwise, non-combusted fuel may get into the catalytic con-
verter and damage it.
X Have the cause rectified immediately at a qualified specialist
workshop. The coolant tempera-
ture display is showing
more than 120
†. The
coolant warning lamp
may also be on and a
warning tone may
sound. The coolant level is too low. The coolant is too hot and the engine
is no longer being cooled sufficiently.
X
Stop as soon as possible and allow the engine and the coolant
to cool down.
X Check the coolant level (Y page 288). Observe the warning
notes as you do so and top up the coolant if necessary. If the coolant level is correct, the engine radiator fan may be faulty.
The coolant is too hot and the engine is no longer being cooled
sufficiently.
X
If the coolant temperature is below 120 †, you can continue
driving to the nearest qualified specialist workshop.
X Avoid heavy loads on the engine as you do so, e.g. driving in
mountainous terrain and stop-start traffic. Manual transmission
Gear lever
! Only engage gear when the clutch pedal
is depressed.
! When shifting to 5th and 6th gear, you
must

press the shift lever to the right. Oth-
erwise, you could shift unintentionally into
3rd or 4th gear and damage the engine or
transmission.
If you shift down at too high a speed (trans-
mission braking), this can cause the engine
to overrev, leading to engine damage.
Do not use the clutch bite point to keep the
vehicle stationary on uphill gradients.
There is otherwise a risk of damaging the
clutch.
! On long and steep downhill gradients,
especially if the vehicle is laden or towing a trailer, you must shift into gear
1, 2 or 3
in
good time. This uses the engine's braking
effect. This relieves the load on the brake
system and prevents the brakes from over-
heating and wearing too quickly. Gear lever
k
Reverse gear
1 to 6 Forward gears150
Manual transmission
Driving and parking

Display messages Possible causes/consequences and
M SolutionsPRE-SAFE
Functions cur‐
rently
limited See
Owner's Manual Adaptive Brake Assist is temporarily inoperative. Possible causes:
R
the radar sensor cover in the radiator trim is dirty.
R the function is impaired due to heavy rain or snow.
R the radar sensor system is temporarily inoperative, e.g. due to
electromagnetic radiation emitted by nearby TV or radio sta-
tions or other sources of electromagnetic radiation.
R AMG vehicles: ESP ®
is deactivated.
R the system is outside the operating temperature range.
R the on-board voltage is too low.
Once
the causes listed above no longer apply, the display message
goes out.
Adaptive Brake Assist is operational again.
If the display message does not disappear:
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 162).
X Clean the radar sensor cover in the radiator grille
(Y page 294).
X Restart the engine.
X AMG vehicles: reactivate ESP ®
(Y page 66). PRE-SAFE
Functions limited
See Owner's Manual Adaptive Brake Assist is faulty. The distance warning signal may
also have failed.
X
Visit a qualified specialist workshop. ü If the symbol appears in the multifunction display, a seat belt
tongue has been inserted into a rear seat belt buckle.
Further

information on the status indicator for the rear seat belts
(Y page 49). ý If the symbol appears in the multifunction display, a seat belt
tongue has not been inserted in a rear seat belt buckle.
G WARNING
A seat belt which is not worn correctly, or which has not been
engaged in the seat belt buckle correctly, cannot provide the
intended level of protection.
This poses an increased risk of injury.
X If necessary, ask the occupants in the rear to fasten their seat
belts ( Y page 47).
Further information on the status indicator for the rear seat belts
(Y page 49). Display messages
237
On-board computer and displays Z

Display messages Possible causes/consequences and
M Solutions?
Coolant Stop vehi‐
cle Switch engine
off The coolant is too hot.
A warning tone also sounds.
G WARNING
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.
Steam
from an overheated engine can cause serious burns, which
can occur just by opening the bonnet.
There is a risk of injury.
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 162).
X Wait until the engine has cooled down.
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 display message goes out
and the coolant temperature is below

120 †. The engine may
otherwise be damaged.
X Pay attention to the coolant temperature display.
X If the temperature increases again, visit a qualified specialist
workshop immediately.
Under normal operating conditions and with the specified coolant
level, the coolant temperature may rise to
120 †.# The battery is not being charged.
A warning tone also sounds.
Possible causes:
R
faulty alternator
R torn poly-V-belt
R a malfunction in the electronics
X Stop the vehicle immediately, paying attention to road and traf-
fic conditions, and switch off the engine.
X Open the bonnet.
X Check whether the poly-V-belt is torn.
If the poly-V-belt is torn:
! Do

not continue driving. The engine could otherwise overheat.
X Consult a qualified specialist workshop.
If the poly-V-belt is OK:
X Visit a qualified specialist workshop immediately.244
Display messages
On-board computer and displays

Display messages Possible causes/consequences and
M SolutionsPark Assist inoper‐
ative You have just carried out a large number of turning or parking
manoeuvres.
Active Parking Assist will become available again after approx-
imately ten minutes (
Y page 186).
X Pull over and stop the vehicle safely as soon as possible, paying
attention to road and traffic conditions.
X Switch off and restart the engine.
If the display message continues to be displayed:
X Visit a qualified specialist workshop. PARKTRONIC is faulty.
X
Visit a qualified specialist workshop. DISTRONIC PLUS off DISTRONIC PLUS has been deactivated (
Y page 173). If it was
deactivated automatically, a warning tone also sounds. DISTRONIC PLUS
available again DISTRONIC PLUS is operational again after having been tempo-
rarily unavailable. You can now reactivate DISTRONIC PLUS
(Y page 173).
DISTRONIC PLUS cur‐
rently
unavailable
See Owner's Manual DISTRONIC PLUS is temporarily inoperative. Possible causes:
R
the function is impaired due to heavy rain or snow.
R the sensors in the radiator trim are dirty
R the radar sensor system is temporarily inoperative, e.g. due to
electromagnetic radiation emitted by nearby TV or radio sta-
tions or other sources of electromagnetic radiation.
R the system is outside the operating temperature range.
R the on-board voltage is too low.
A warning tone also sounds.
Once
the causes listed above no longer apply, the display message
goes out.
DISTRONIC is operational again.
If the display message does not disappear:
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 162).
X Clean the sensors in the radiator trim (Y page 294).
X Restart the engine. Display messages
249
On-board computer and displays Z

Problem Possible causes/consequences and
M Solutions?
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 mal-
functioning.
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 162).
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 (Y page 288).
Observe the warning notes as you do so.
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 heavy loads on the engine 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.
Steam from an overheated engine can cause serious burns which
can occur just by opening the bonnet.
This poses 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 162).Warning and indicator lamps in the instrument cluster
265
On-board computer and displays Z

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 top up the coolant (Y page 288).
Observe the warning notes as you do so.
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 If the coolant temperature is below 120 †, you can continue
driving to the nearest qualified specialist workshop.
X Avoid heavy loads on the engine as you do so, e.g. driving in
mountainous terrain and stop-start traffic. Driving systems
Problem Possible causes/consequences and
M Solutions·
The red distance warn-
ing
lamp lights up while
the vehicle is in motion. The distance to the vehicle in front is too small for the speed
selected.
X
Increase the distance. ·
The red distance warn-
ing

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.266
Warning and indicator lamps in the instrument cluster
On-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). Engine compartment
Bonnet
Important safety notes G
WARNING
An unlocked bonnet may open while driving
and
block your view. There is a risk of an acci-
dent.
Never unlock the bonnet while driving. G
WARNING
When being opened and closed, the bonnet
may suddenly fall into the closed position.
There

is a risk of injury to persons in the range
of movement of the bonnet.
Open and close the bonnet only when nobody
is in the range of movement. G
WARNING
Certain components in the engine compart-
ment could be very hot, e.g. the engine, the
radiator and parts of the exhaust system.
There is a risk of injury when accessing the
engine compartment.
As far as possible, allow the engine to cool
down and only touch the following compo-
nents. G
WARNING
If you open the bonnet while the engine is
overheating or while there is a fire in the engine compartment, you could come into
contact with hot gases or other leaking
service products. There is a danger of injury.
Allow an overheating engine to cool down
before

opening the bonnet. If there is a fire in
the engine compartment, leave the bonnet
closed and notify the fire brigade. G
WARNING
There are parts in the engine compartment
that
move. Certain components may continue
to run even if the ignition is switched off or
may suddenly start again, e.g. the radiator
fan. There is a danger of injury.
If you need to access the engine compart-
ment:
R switch off the ignition
R never enter the danger area of moving com-
ponents, e.g. the rotation area of the fan
R keep items of clothing away from moving
parts G
WARNING
The ignition system and the fuel injection sys-
tem operate with a high voltage. If you touch
the live components, you could receive an
electric shock. There is a danger of injury.
Never touch components of the ignition sys-
tem or the fuel injection system when the
ignition is switched on.
Active bonnet (pedestrian protection) Operating principle
!
Once

triggered, an active bonnet must be
reset at a qualified specialist workshop,
e.g. a Mercedes-Benz Service Centre. The
active bonnet function will then be availa-
ble again. The additional pedestrian pro-
tection provided by the active bonnet will
then be restored.
The active bonnet is only available in certain
countries.
The active bonnet can reduce the risk of injury
to pedestrians in certain accident situations. 284
Engine compartment
Maintenance and care

Raising the active bonnet increases the clear-
ance
to hard components, such as the engine.
If the active bonnet has been triggered, it is
raised at the rear in the area around the hinge
by approximately 60 mm.
For the drive to the workshop, reset the trig-
gered active bonnet yourself. If the active
bonnet has been triggered, pedestrian pro-
tection may be limited.
Resetting G
WARNING
Certain components in the engine compart-
ment could be very hot, e.g. the engine, the
radiator and parts of the exhaust system.
There is a risk of injury when accessing the
engine compartment.
As far as possible, allow the engine to cool
down and only touch the following compo-
nents. X
With your hand flat, push down active bon-
net : in the area around the hinges on
both

sides (arrows) until you feel it engage.
If you can raise the active bonnet slightly in
the
area around the hinges, it is not engaged
correctly. Repeat the step.
If the bonnet can then still be raised, drive
directly to a qualified specialist workshop. Do
not drive faster than 100 km/h. Opening the bonnet G
WARNING
When the bonnet is open, and the windscreen
wipers are set in motion, you can be injured
by the wiper linkage. There is a risk of injury.
Always switch off the windscreen wipers and
the ignition before opening the bonnet.
! Make

sure that the windscreen wipers are
not folded away from the windscreen. Oth-
erwise, you could damage the windscreen
wipers or the bonnet. X
Make sure that the windscreen wipers are
switched off.
X Pull release lever : on the bonnet.
The bonnet is released. X
Reach into the gap between the bonnet and
the radiator trim and press bonnet catch
lever ; to the left.
X Raise the bonnet. Engine compartment
285
Maintenance and care Z