ECU MERCEDES-BENZ A CLASS 2012 Owner's Manual

DISTRONIC PLUS is automatically deactiva-
ted if:
R
you apply the electric parking brake or if
the vehicle is automatically secured with
the electric parking brake
R you are driving slower than
10 km/h and
there is no longer a vehicle in front, or if the
vehicle in front is no longer detected
R ESP ®
intervenes or you deactivate ESP ®
R the transmission is in the P, R or N position
R you switch off the radar sensor system
R you pull the cruise control lever towards
you in order to pull away and the front-
passenger door or one of the rear doors is
open
R the vehicle is skidding
R you activate Active Parking Assist
If DISTRONIC PLUS is deactivated, you will
hear a warning tone. You will see the DIS‐
TRONIC PLUS off message in the multifunc-
tion display for approximately five seconds.
In the Assistance menu (Y page 217) of the
on-board computer, you can select the assis-
tance graphic. :
Vehicle in front, if detected
; Distance indicator: current distance to
the vehicle in front
= Specified minimum distance to the vehi-
cle in front; adjustable
? Own vehicle
X Select the Distance display function
using the on-board computer
(Y page 217). Tips for driving with DISTRONIC PLUS General notes
The

following contains descriptions of certain
road and traffic conditions in which you must
be particularly attentive. In such situations,
brake if necessary. DISTRONIC PLUS is then
deactivated.
Cornering, going into and coming out of a
bend The ability of DISTRONIC PLUS to detect vehi-
cles when cornering is limited. Your vehicle
may brake unexpectedly or late.
Vehicles

which are not driving in the mid-
dle of their lane DISTRONIC PLUS may not detect vehicles
which are not driving in the middle of their
lane. The distance to the vehicle in front will
be too short.178
Driving systems
Driving and parking

Other vehicles changing lane
DISTRONIC PLUS has not detected the vehi-
cle
cutting in yet. The distance to this vehicle
will be too short.
Narrow vehicles DISTRONIC PLUS has not yet detected the
vehicle in front on the edge of the carriage-
way, because of its narrow width. The dis-
tance

to the vehicle in front will be too short.
Obstructions and stationary vehicles DISTRONIC PLUS does not brake for obsta-
cles

or stationary vehicles. If, for example, the detected vehicle turns a corner and reveals
an

obstacle or stationary vehicle, DISTRONIC
PLUS will not brake for these.
Crossing vehicles DISTRONIC PLUS may detect vehicles that
are

crossing your lane by mistake. Activating
DISTRONIC PLUS at traffic lights with cross-
ing traffic, for example, could cause your vehi-
cle to pull away unintentionally. HOLD function
Important safety notes G
WARNING
When leaving the vehicle, it can still roll away
despite
being braked by the HOLD function if:
R there is a malfunction in the system or in
the voltage supply
R the HOLD function is deactivated by the
accelerator pedal being depressed, e.g. by
a vehicle occupant
R the electrical system in the engine com-
partment, the battery or the fuses are tam-
pered with
R the battery is disconnected
There is a risk of an accident.
Before leaving the vehicle, always deactivate
the HOLD function and secure the vehicle
from rolling away. Driving systems
179
Driving and parking Z

!
If DISTRONIC PLUS or the HOLD function
is activated, the vehicle brakes automati-
cally in certain situations. To prevent dam-
age to the vehicle, deactivate DISTRONIC
PLUS and the HOLD function in the follow-
ing or other similar situations:
R when towing the vehicle
R in the car wash
Deactivate the HOLD function (Y page 180).
General notes The HOLD function can assist the driver in the
following situations:
R
when pulling away, especially on steep
slopes
R when manoeuvring on steep slopes
R when waiting in traffic
The vehicle is kept stationary without the
driver having to depress the brake pedal.
The

braking effect is cancelled and the HOLD
function is deactivated when you depress the
accelerator pedal to pull away.
Activation conditions You can activate the HOLD function if:
R
the vehicle is stationary
R the

engine is running or if it has been auto-
matically switched off by the ECO start/
stop function
R the driver's door is closed or if your seat
belt is fastened
R the electric parking brake is released
R the transmission is in position D, R or N on
vehicles with automatic transmission
R DISTRONIC PLUS is deactivated Activating the HOLD function Example: vehicles with colour multifunction display
X
Make sure that the activation conditions
are met.
X Depress the brake pedal.
X Quickly depress the brake pedal further
until : appears in the multifunction dis-
play.
The HOLD function is activated. You can
release the brake pedal.
i If depressing the brake pedal the first
time does not activate the HOLD function,
wait briefly and then try again.
Deactivating the HOLD function The HOLD function is deactivated automati-
cally if:
R
you

accelerate. On vehicles with automatic
transmission: only when the transmission
is in position D or R.
R the transmission is in position P on vehicles
with automatic transmission.
R you depress the brake pedal again with a
certain amount of pressure until : disap-
pears from the multifunction display.
R you secure the vehicle using the electric
parking brake.
R you activate DISTRONIC PLUS.
i After a short period the vehicle is secured
by the electric parking brake, thus relieving
the service brake. 180
Driving systems
Driving and parking

The electric parking brake secures the vehicle
automatically if the HOLD function is activa-
ted and:
R
the driver's door is open and the driver's
seat belt is unfastened
R the
engine is switched off, unless it is auto-
matically switched off by the ECO start/
stop function
R a system fault occurs
R the power supply is not sufficient
Vehicles with automatic transmission
If a fault occurs, then the transmission may
also be shifted into position P automatically.
Vehicles with manual transmission
The Brake immediately message can also
appear in the multifunction display.
X Immediately depress the brake pedal firmly
until

the warning message in the multifunc-
tion display goes out.
The HOLD function is deactivated.
A horn will sound at regular intervals if you
turn off the engine, take off your seat belt or
open the driver's door when the HOLD func-
tion is activated. The horn alerts you to the
fact that the HOLD function is still activated.
If you attempt to lock the vehicle, the tone
becomes louder. The vehicle cannot be
locked until you have deactivated the HOLD
function.
i Once you have switched off the engine,
you cannot restart it until you have deacti-
vated the HOLD function. RACE START
Important safety notes RACE START enables optimum acceleration
from a standing start. The precondition for
this is a suitable high-grip road surface.
Only

activate RACE START on dedicated race
circuits. i
RACE
START is only available in AMG vehi-
cles.
Activation conditions You can activate RACE START if:
R
the doors, the bonnet and the tailgate are
closed
R the

engine is running and the transmission,
traction control and engine are at operating
temperature
R SPORT handling mode is activated
(Y page 66)
R the steering wheel is in the straight-ahead
position.
R the vehicle is stationary and the brake
pedal is depressed (left foot)
R the transmission is in position D.
R drive program M is selected ( Y page 155).
Activating RACE START X
Depress the brake pedal with your left foot
and keep it depressed.
X Pull and hold both steering wheel gearshift
paddles.
X The RACE START Confirm: Paddle UP
Cancel: Paddle DOWN message appears
in the multifunction display.
X Release both steering wheel gearshift pad-
dles.
i If the activation conditions are no longer
fulfilled, RACE START is cancelled. The
RACE START not possible See Own‐
er's

Manual message appears in the mul-
tifunction display.
X To cancel:
pull the left steering wheel shift
paddle (Y page 156).
or
X To confirm: pull the right steering wheel
shift paddle

(Y page 156).
The RACE START available Depress
accelerator message appears in the mul-
tifunction display. Driving systems
181
Driving and parking Z

the vehicle and the trailer drawbar. This poses
a risk of injury.
Do not uncouple a trailer with an engaged
overrun brake.
! Do not disconnect a trailer with an
engaged overrun brake. Otherwise, your
vehicle
could be damaged by the rebound-
ing of the overrun brake.
! Remove the installed adapter cable
before folding in the ball coupling. Other-
wise, damage may occur to the rear
bumper and the adapter cable.
X Make sure that the transmission is in posi-
tion P.
X Apply the electric parking brake.
X Secure the trailer against rolling away.
X Remove the trailer cable and decouple the
trailer. Folding in the ball coupling
G
WARNING
If you release the ball coupling or it does not
engage
correctly when folding in, it will swing
out. Within pivoting range of the ball coupling,
there is an increased risk of an accident and
injury.
Only release the ball coupling if the pivoting
range is unobstructed. Always make sure that
the ball coupling engages when folding in.
X Fold the ball coupling back in if you are not
using the trailer tow hitch.
X Place the protective covering on the ball
coupling.
The release wheel is located behind the left-
hand side trim panel in the boot. X
To open the cover: turn handle : anti-
clockwise and fold down cover ; and
remove it. X
Pull out release wheel =.
X Turn release wheel =
anti-clockwise as far
as it will go.
The ball coupling disengages and folds out
behind the rear bumper. Indicator
lamp ? flashes. Towing a trailer
205
Driving and parking Z

X
Press the ball coupling in the direction of
the arrow until it engages behind the
bumper.
Indicator lamp ? goes out and the mes-
sage in the multifunction display disap-
pears. Trailer power supply
! You can connect accessories with a
power rating of up to 240 W to the perma-
nent
power supply and with a power rating
of up to 180 W to the power supply that is
switched on via the ignition lock.
The trailer battery may not be charged from
the power supply.
X To switch the connected power supply
on or off: turn the key in the ignition lock
to position 2 or 0 respectively.
When it leaves the factory, your vehicle's
trailer socket is equipped with a permanent
power supply and a power supply that is
switched on via the ignition lock.
The permanent power supply is supplied via
trailer socket pin 9.
The power supply that is switched on via the
ignition lock is supplied via trailer socket pin
10.
The trailer's permanent power supply is
switched

off in the event of low vehicle supply
voltage and after six hours at the latest.
You can find more information about instal-
ling the trailer electrics at a qualified special-
ist workshop. Bulb failure indicator for LED lamps
i If LED lamps are fitted in the trailer, an
error message may appear in the multi-
function

display even if there is no fault. The
reason for the error message could be that
the current has fallen below the minimum
of 50 mA. To ensure reliable operation of the bulb failure
indicator,

each LED chain in the trailer lighting
must be guaranteed a minimum current of
50 mA. Trailer with 7-pin connector
General notes Trailer with 7-pin connector: you can con-
nect

to the 13-pin socket on the ball coupling
using an adapter or, if necessary, an adapter
cable. Both can be obtained at a qualified
specialist workshop.
Fitting the adapter !
Make sure that there is sufficient cable
play so that the cable cannot become
detached when cornering.
! Remove the installed adapter cable
before folding in the ball coupling. Other-
wise, damage may occur to the rear
bumper and the adapter cable. X
Open the socket cover.
X Insert the plug connector with lug : into
groove =

on the socket. Turn bayonet con-
nection ; clockwise to the stop.
X Let the cover engage.
X If you are using an adapter cable, secure
the cable to the trailer with cable ties.206
Towing a trailer
Driving and parking

Display messages Possible causes/consequences and
M SolutionsThe red
! indicator lamp flashes and the yellow ! warning
lamp is lit.
The electric parking brake is malfunctioning.
To release:
X Switch off the ignition and turn it back on.
X Release the electric parking brake manually.
To apply:
X Switch off the ignition and turn it back on.
X Apply the electric parking brake manually.
If the red ! indicator lamp continues to flash:
X Do not drive on.
X Secure the vehicle against rolling away ( Y page 325).
X Vehicles with manual transmission: engage first gear.
X Vehicles with automatic transmission:
shift the transmission
to P.
X Turn the front wheels towards the kerb.
X Consult a qualified specialist workshop. The yellow
! warning lamp lights up. The red ! 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.
X Switch off the ignition and turn it back on.
X Apply the electric parking brake.
If it is not possible to apply the electric parking brake:
X Vehicles with manual transmission: engage first gear.
X Vehicles with automatic transmission:
shift the transmission
to P.
X Visit a qualified specialist workshop.
If it is not possible to release the electric parking brake:
X Vehicles with manual transmission (automatic emergency
release): insert the seat belt in the belt buckle and accelerate
slightly more when pulling away.
X Vehicles with automatic transmission: release the electric
parking brake automatically

(Y page 163).
If the electric parking brake still cannot be released:
X Consult a qualified specialist workshop.234
Display messages
On-board computer and displays

Display messages Possible causes/consequences and
M SolutionsJ
Brake immediately Vehicles with manual transmission: a malfunction has occurred
while the HOLD function was activated.
A
tone may also sound at regular intervals. If you attempt to lock
the vehicle, the tone becomes louder.
You cannot start the engine.
X Paying attention to the traffic situation, immediately depress the
brake pedal firmly and hold until the display message disap-
pears.
X Secure the vehicle against rolling away ( Y page 162).
You can restart the engine. J
Check brake fluid
level There is insufficient brake fluid in the brake fluid reservoir.
In

addition, the red J warning lamp lights up in the instrument
cluster and a warning tone sounds.
G WARNING
The 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 162).
X Consult a qualified specialist workshop.
X Do not top up the brake fluid. This does not correct the fault. #
Check brake pad
wear The brake pads/linings have reached their wear limit.
X
Visit a qualified specialist workshop. PRE-SAFE
inoperative See
Owner's Manual
Important functions of PRE-SAFE
®

have failed. All other occupant
safety systems, e.g. airbags, remain available.
X Visit a qualified specialist workshop immediately.236
Display messages
On-board computer and displays

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