Page 289 of 489

Coupling up a trailer
X Make sure that the transmission is in posi-
tion P.
X Apply the electric parking brake.
X Position the trailer horizontally behind the
vehicle.
X Couple up the trailer.
X Establish the electric connection between
the vehicle and the trailer.
X Check that the trailer lighting system is
working.
X Push the combination switch upwards/
downwards and check whether the corre-
sponding turn signal on the trailer is flash-
ing.
A connected trailer is only recognised when the electrical connection is established
correctly and when the lighting system is
working properly. The functioning of other
systems, e.g. ESP ®
, PARKTRONIC, Active
Parking Assist, Active Blind Spot Assist or
Lane Keeping Assist also depends on this. Uncoupling a trailer
G
WARNING
If you uncouple a trailer with an engaged over- run brake, you could trap your hand between
the vehicle and the trailer drawbar. This poses a risk of injury.
Do not uncouple a trailer with an engaged
overrun brake. G
WARNING
Vehicles with level control:
If you disconnect the trailer cable, the vehicle is lowered. This can cause you or others to
become trapped between the vehicle body
and tyres, or underneath the vehicle. This
poses a risk of injury.
Make sure that no-one is in the immediate
vicinity of the wheel arch or underneath the
vehicle when disconnecting the trailer cable. !
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.
Fold the ball coupling back in if you are not
using the trailer tow hitch. X Make sure that the vehicle is stationary and
the trailer cables are disconnected.
X Place the protective covering on the ball
coupling.
X Open the boot lid. 286
Towing a trailerDriving and parking
Page 290 of 489

X
Pull release knob :until the ball coupling
unlocks.
The ball coupling folds down from under the rear bumper. The indicator lamp on the
release knob flashes.
Do not attempt to speed this process up by
applying additional pressure with your foot. The system could otherwise be mechani-
cally damaged. X
Press the ball coupling in the direction of
the arrow until it engages audibly behind
the bumper.
The indicator lamp on the release knob
goes out and the message in the multifunc-
tion display disappears. 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.
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 fitting
the trailer electrics at a qualified specialist
workshop.
X To switch the connected power supply
on or off: turn the key in the ignition lock to
position 2or 0respectively (Y page 181). Bulb failure indicator for LED lamps
If LED lamps are fitted in the trailer, an error
message may appear in the multifunction dis-
play even if there is no fault. The reason for
the error message may 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. Towing a trailer
287Driving and parking Z
Page 291 of 489
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. 288
Towing a trailerDriving and pa
rking
Page 292 of 489
Problems with trailer towing
Problem
Possible causes/consequences and
M
MSolutions The released ball cou-
pling cannot be
engaged. X
Visit a qualified specialist workshop. The ball coupling does
not unlock, even
though:
R the vehicle is station-
ary
R no trailer cable is
connected
R the release knob to
unlock the ball cou-
pling has been pulled
for more than a sec-
ond. The on-board voltage is insufficient.
X Start the engine.
If the ball coupling still does not unlock: X Visit a qualified specialist workshop. Towing a trailer
289Driving and parking Z
Page 293 of 489
Page 294 of 489
Useful information
............................292
Important safety notes .....................292
Displays and operation .....................292
Menus and submenus ......................297
Display messages ............................. 314
Warning and indicator lamps in the instrument cluster ............................351 291On-board computer and displays
Page 295 of 489

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 27). Important safety notes
G
WARNING
Operating the integrated information systems and communications equipment in the vehicle
while driving will distract you from traffic con-
ditions. You could then lose control of the
vehicle. There is a risk of an accident.
Only operate these devices if road traffic con-
ditions permit. If you are unsure about the
surrounding conditions, pull over to a safe
location and make entries only while the vehi-
cle is stationary.
You must observe the legal requirements for
the country in which you are currently driving when operating the on-board computer. G
WARNING
If the instrument cluster has failed or mal-
functioned, you may not recognise function
restrictions relevant to safety. The operating
safety of your vehicle may be impaired. There is a risk of an accident.
Drive on carefully. Have the vehicle checked
at a qualified specialist workshop immedi-
ately.
The on-board computer only shows messages
or warnings from certain systems in the mul- tifunction display. You should therefore make
sure your vehicle is operating safely at all times. Otherwise, a vehicle that is not oper-
ating safely may cause an accident.
If the operating safety of your vehicle is
impaired, park the vehicle safely as soon as
possible. Contact a qualified specialist work-
shop.
For an overview, see the instrument cluster
illustration (Y
page 34). Displays and operation
Instrument cluster lighting
The lighting in the instrument cluster, in the
displays and the controls in the vehicle inte-
rior can be adjusted using brightness control
knob :.
X Turn brightness control knob :up or
down.
If the light switch (Y page 137) is set to
Ã, TorL the brightness is
dependent upon the brightness of the
ambient light.
i The light sensor in the instrument cluster
automatically controls the brightness of
the multifunction display.
In daylight, the displays in the instrument
cluster are illuminated. A dimming function
is not possible in daylight. 292
Displays and operationOn-board computer and displays
Page 296 of 489

Speedometer with segments
The segments in the speedometer indicate
which speed range is available.
R Cruise control activated (Y page 216):
The segments light up from the stored
speed to the maximum speed.
R Variable SPEEDTRONIC activated
(Y page 219):
The segments light up from the start of the
scale to the selected limit speed.
R DISTRONIC PLUS activated (Y page 222):
One or two segments in the set speed
range light up.
R DISTRONIC PLUS detects a vehicle in front:
The segments between the speed of the
vehicle in front and the stored speed light
up. Rev counter
! Do not drive in the overrevving range.
Doing so will damage the engine.
The red band in the rev counter indicates the engine's overrevving range.
The fuel supply is interrupted to protect the
engine when the red band is reached. Outside temperature display
You should pay special attention to road con-
ditions when temperatures are around the
freezing point.
Bear in mind that the outside temperature
display indicates the temperature measured
and does not record the road temperature.
The outside temperature display is in the mul- tifunction display (Y page 295).
Changes in the outside temperature are dis-
played after a short delay. Coolant temperature gauge
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 ser-
vice 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.
The analogue coolant temperature gauge is in
the instrument cluster on the right-hand side (Y page 34).
In the on-board computer in the Service Service
menu there is a digital coolant temperature
gauge (Y page 307).
Under normal operating conditions and with
the specified coolant level, the coolant tem-
perature may rise to 120 †.
At high outside temperatures and when driv-
ing uphill, the coolant temperature may rise
to the end of the scale. Displays and operation
293On-board computer and displays Z