
A connected trailer is only detected when the
electrical connection is established correctly
and the lighting system is working properly. The
function of other systems also depends on this, for example:
R ESP ®
R PARKTRONIC
R Active Parking Assist
R Active Blind Spot Assist
R Active Lane Keeping Assist 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 rebounding of the overrun
brake.
! Remove the installed adapter cable before
folding in the ball coupling. Otherwise, dam-
age may occur to the rear bumper and the
adapter cable.
X Apply the electric parking brake manually.
X Vehicles with manual transmission:
depress the clutch pedal fully and engage first
or reverse gear.
X Vehicles with automatic transmission:
shift the transmission to position P.
X Switch off the engine. X
Secure the vehicle and trailer against rolling
away.
X Remove the trailer cable and uncouple the
trailer. Trailer power supply
! You can connect accessories to the perma-
nent power supply up to a maximum of 240 W.
You cannot charge a trailer battery using 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 on-board voltage and after six hours at the latest.
You can find more information about installing
the trailer electrics at a qualified specialist work- shop.
To activate the switched power supply:
X Turn the key to position 2in the ignition lock
(Y page 133).
or X Press the Start/Stop button twice on vehicles
with KEYLESS-GO or the KEYLESS-GO start
function (Y page 133).
To deactivate the switched power supply: X Turn the key to position 0in the ignition lock
(Y page 133).
or X Press the Start/Stop button once on vehicles
with KEYLESS-GO or the KEYLESS-GO start
function (Y page 133). Failure check for LEDs
If LED lamps are fitted in the trailer, a malfunc-
tion message may appear in the multifunction
display 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. 216
Towing a trailerDriving an
d parking

Display messages
Possible causes/consequences and
M
MSolutions Without changing
Without changing
gear, consult work‐ gear, consult work‐
shop shop You cannot change the transmission position due to a malfunction.
A warning tone also sounds.
If transmission position
Dis selected:
X Drive to a qualified specialist workshop without shifting the trans-
mission from position D.
If transmission position R,Nor Pis selected:
X Secure the vehicle against rolling away (Y page 159).
X Consult a qualified specialist workshop. Reversing Reversing
not
not poss.
poss.
Consult workshop
Consult workshop You can no longer shift to transmission position
Rdue to a malfunc-
tion.
The transmission positions P,Nor Dcontinue to be available.
A warning tone also sounds.
X Consult a qualified specialist workshop. Transmission Mal‐ Transmission Mal‐
function Stop function Stop A malfunction has occurred in the mechanical transmission compo-
nents.
A warning tone also sounds. The transmission shifts automatically to position N.
X Stop the vehicle, paying attention to road and traffic conditions.
X Shift the transmission to position P.
X Secure the vehicle against rolling away (Y page 159).
X Consult a qualified specialist workshop. Stop vehicle Leave Stop vehicle Leave
engine engine
running
running Wait
Wait
Transmission cool‐
Transmission cool‐
ing ing The transmission has overheated. Pulling away can be temporarily
impaired or not possible.
X Stop the vehicle safely as soon as possible, paying attention to road
and traffic conditions. Do not continue driving.
X Leave the engine running.
X Wait until the display message disappears before pulling away. Depress clutch
Depress clutch
fully to start fully to start
engine engine You have attempted to start the engine without depressing the clutch
pedal.
X Depress the clutch pedal.
X Restart the engine. The engine has stalled while pulling away, e.g. because the clutch
pedal was released too quickly.
X Depress the clutch pedal again.
The engine starts automatically.
X Slowly release the clutch pedal to pull away. 268
Display
messagesOn-board computer and displays

Display messages
Possible causes/consequences and
M
MSolutions Clutch overheated
Clutch overheated
Avoid pulling away Avoid pulling away
Engage/disengage Engage/disengage
clutch quickly if clutch quickly if
req. req. The clutch is under considerable load and the permitted operating
temperature has been exceeded. A warning tone also sounds.
Avoid frequent pulling away and driving at walking pace over longer
distances.
X Stop the vehicle, paying attention to road and traffic conditions.
X Secure the vehicle against rolling away (Y page 159).
X Leave the engine running.
The clutch is cooled more quickly with the engine running.
or X If possible, drive on at a steady speed.
X Remove your foot from the clutch pedal and do not allow the clutch
to slip.
The clutch may also cool down during the journey.
It may take several minutes for it to cool down. When the clutch has
cooled down, the display message disappears. The clutch is fully
operational again. N The boot lid is open.
X Close the boot lid. M The bonnet is open. A warning tone also sounds.
G WARNING
The open bonnet may then block your view when the vehicle is in
motion.
There is a risk of an accident.
X Stop the vehicle safely as soon as possible, paying attention to road
and traffic conditions.
X Secure the vehicle against rolling away (Y page 159).
X Close the bonnet. Active bonnet mal‐ Active bonnet mal‐
function See Own‐ function See Own‐
er's Manual er's Manual The active bonnet (pedestrian protection) is not active due to a mal-
function or because it has already been triggered.
X Consult a qualified specialist workshop. C At least one door is open. A warning tone also sounds.
X Close all doors. _
Front left seat Front left seat
backrest backrest
not
notlocked
locked
or Front right seat
Front right seat
backrest not locked
backrest not locked The driver's or front-passenger's seat backrest is not engaged. A
warning tone also sounds.
X Push the backrest back until it engages. Display
messages
269On-board computer and displays Z

G
WARNING
A discharged battery can freeze at temperatures below freezing point. When jump-starting the
vehicle or charging the battery, gases can escape from the battery. There is a risk of an explosion.
Allow the frozen battery to thaw out before charging it or jump-starting.
If the warning and indicator lamps do not light up on the instrument cluster when temperatures are low, it is probably because the discharged battery has frozen. In this case, you may neither jump-
start the vehicle nor charge the battery. The service life of a battery that has been thawed may be
reduced. The starting characteristics may be impaired, especially at low temperatures. Have the
thawed battery checked at a qualified specialist workshop.
All vehicles:
! Vehicles with a petrol engine:
avoid repeated and lengthy starting attempts. Otherwise, the
non-combusted fuel may damage the catalytic converter.
Do not use a rapid charging device to start the vehicle. If your vehicle's battery is discharged, the
engine can be jump-started from another vehicle or from a second battery using jump leads.
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 donor battery or a jump-starting device.
R Vehicles with a petrol engine: jump-start the vehicle only when the engine and exhaust system
are cold.
R All vehicles except vehicles with a lithium-ion battery: do not start the engine if the battery
is frozen. Let the battery thaw first.
R Jump-starting may be performed only using batteries with a nominal voltage of 12 V.
R Use only jump leads that 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 empty battery a little.
R Make sure that the two vehicles do not touch.
Make sure that:
R The jump leads are not damaged.
R Non-insulated parts of the terminal clamps do not come into contact with other metal parts while
the jump leads are connected to the battery.
R The jump leads cannot come into contact with parts that 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 Automatic transmission: shift the transmission to position P.
X Manual transmission: depress the clutch pedal fully and engage neutral.
X Make sure that the ignition is switched off . All indicator lamps on the instrument cluster must be
off. When using the key, turn the key to position 0in the ignition lock and remove it (Y page 133).
X Switch off all electrical consumers, e.g. rear window heating, lighting etc.
X Open the bonnet. 334
Jump-startingBreakdown assistance

Vehicles with 4MATIC may either be towed with
both axles on the ground or be loaded and trans- ported.
! Vehicles with automatic transmission must
not be towed with the rear axle raised. The
car/trailer combination may otherwise
swerve or even overturn.
! The ignition must be switched off if you are
towing the vehicle with the rear axle raised.
Intervention by ESP ®
could otherwise dam-
age the brake system.
X Switch on the hazard warning lamps
(Y page 116).
X Move the front wheels to the straight-ahead
position.
X If necessary, turn the key to position 0in the
ignition lock and remove the key from the
ignition lock.
X When leaving the vehicle, take the key with
you. Towing the vehicle with all wheels on
the ground
Vehicles with automatic transmission: the
automatic transmission automatically shifts to
position Pwhen you open the driver's or front-
passenger door or when you remove the key
from the ignition lock. In order to ensure that the
automatic transmission stays in position N
when the vehicle is being towed, you must
observe the following points:
X Make sure that the vehicle is stationary.
X Turn the key to position 2in the ignition lock.
X Depress the brake pedal and keep it
depressed.
X Shift the automatic transmission to position
N.
Vehicles with manual transmission: X Turn the key to position 2in the ignition lock.
X Depress the brake pedal and keep it
depressed.
X Depress the clutch pedal fully and shift to
neutral.
All vehicles:
X Leave the key in position 2in the ignition lock.
X Release the brake pedal. X
Release the electric parking brake.
X Switch on the hazard warning lamps
(Y page 116).
In order to signal a change of direction when
towing the vehicle with the hazard warning
lamps switched on, use the combination switch
as usual. In this case, only the turn signals for
the desired direction flash. When you reset the
combination switch, the hazard warning lamps
start flashing again. Transporting the vehicle
4MATIC vehicles/vehicles with auto-
matic transmission !
When the vehicle is loaded for transport, the
front and rear axles must be stationary and on
the same transportation vehicle. Positioning
over the connection point of the transport
vehicle is not permitted. The drive train may
otherwise be damaged.
All vehicles !
You may only secure the vehicle by the
wheels, not by parts of the vehicle such as
axle or steering components. Otherwise, the
vehicle could be damaged.
The towing eye or trailer tow hitch can be used
to pull the vehicle onto a trailer or transporter if you wish to transport it.
X Vehicles with manual transmission:
depress the clutch pedal fully and engage
neutral.
X Vehicles with automatic transmission:
turn the key to position
2in the ignition lock.
X Shift the automatic transmission to position
N. 338
Towing away and tow-startingBreakdown assistance

As soon as the vehicle is loaded:
X Secure the vehicle against rolling away by
applying the electric parking brake.
X Vehicles with manual transmission: fully
depress the clutch pedal and engage first or
reverse gear.
X Vehicles with automatic transmission:
shift the automatic transmission to position
P.
X Turn the key to position 0in the ignition lock
and remove it.
X Secure the vehicle. Notes for 4MATIC vehicles
! Vehicles with 4MATIC must not be towed
with the front or rear axle raised; otherwise,
the transmission may be damaged.
Vehicles with 4MATIC may either be towed away
with both axles on the ground or be loaded up
and transported.
If the vehicle has transmission damage or dam- age to the front or rear axle, have it transportedon a transporter or trailer.
In the event of damage to the electrical sys-
tem: if the battery is defective, the automatic
transmission will be locked in position P. To shift
the automatic transmission to position N, you
must provide power to the vehicle's electrical
system in the same way as when jump-starting
(Y page 333).
Have the vehicle transported on a transporter or
trailer. Tow-starting (emergency engine
starting)
! Do not tow-start vehicles with automatic
transmission. You could otherwise damage
the automatic transmission.
i You can find information on "Jump-starting"
under (Y page 333).
Before tow-starting, the following conditions
must be fulfilled:
R the battery is connected
R the engine has cooled down
R the exhaust system has cooled down When tow-starting, it is important that you
observe the safety notes (Y
page 336) and the
legal requirements in each respective country.
X Switch on the hazard warning lamps
(Y page 116).
X Fit the towing eye (Y page 337).
X Secure the rigid towing bar or the towing
rope.
X Depress the brake pedal and keep it
depressed.
X Turn the key to position 2in the ignition lock.
X Depress the clutch pedal fully, engage 2nd
gear and continue to keep the clutch pedal
fully depressed.
X Release the brake pedal.
X Tow-start the vehicle.
X Release the clutch pedal slowly; do not
depress the accelerator pedal while doing so.
X When the engine has been started, immedi-
ately depress the clutch pedal fully and shift
to neutral.
X Pull over at a suitable place and stop the vehi-
cle safely, paying attention to road and traffic
conditions.
X Use the electric parking brake to secure the
vehicle and prevent it from rolling away.
X Remove the rigid towing bar or towing rope.
X Remove the towing eye (Y page 337).
X Switch off the hazard warning lamps. Fuses
Important safety notes
G
WARNING
If you manipulate, bridge or replace a faulty
fuse with a fuse of a higher amperage, the
electric cables could be overloaded. This may result in a fire. There is a risk of an accident
and injury.
Always replace faulty fuses with specified newfuses of the correct amperage.
Blown fuses must be replaced with fuses of the same rating, which you can recognise by the
colour and fuse rating. The fuse ratings are listed
in the fuse allocation chart.
The fuse allocation chart is on the fuse box in the boot (Y page 341). Fuses
339Breakdown assistance Z

!
On vehicles fitted with a tyre pressure mon-
itor, electronic components are located in the wheel.
Tyre-fitting tools should not be applied in thearea of the valve, as this could damage the
electronic components.
Only have tyres changed at a qualified spe-
cialist workshop.
Interchanging the front and rear wheels of dif-
fering dimensions can render the general oper-
ating permit invalid.
Observe the instructions and safety notes in the "Fitting a wheel" section (Y page 351).
The wear patterns on the front and rear tyres
differ depending on the operating conditions.
Interchange the wheels before a clear wear pat-
tern has formed on the tyres. Front tyres typi-
cally wear more on the shoulders, while rear
tyres wear more in the centre.
On vehicles that have front and rear wheels of
the same size, you can interchange the wheels
every 5,000 to 10,000 km depending on the
degree of tyre wear. Ensure the direction of
rotation is maintained.
Clean the contact surfaces of the wheel and the
brake disc thoroughly every time a wheel is
interchanged. Check the tyre pressure and, if
necessary, restart the tyre pressure loss warn-
ing system (Y page 347) or the tyre pressure
monitor (Y page 349). Direction of rotation
Tyres with a specified direction of rotation have additional benefits, e.g. if there is a risk of aqua- planing. These advantages can only be gained if
the tyres are fitted corresponding to the direc-
tion of rotation.
An arrow on the sidewall of the tyre indicates its correct direction of rotation. Storing wheels
Store wheels in a cool, dry and preferably dark
place if they are not being used. Protect the
tyres against oil, grease, petrol and diesel. Fitting a wheel
Preparing the vehicle X
Stop the vehicle on solid, non-slippery and
level ground.
X Apply the electric parking brake manually.
X Move the front wheels to the straight-ahead
position.
X Vehicles with manual transmission:
depress the clutch pedal fully and engage first
or reverse gear.
X Vehicles with automatic transmission:
shift the transmission to position
P.
X Make sure that the vehicle level is set to "Nor-
mal" on vehicles with AIRMATIC (Y page 182).
X Switch off the engine.
X Vehicles without KEYLESS-GO: remove the
key from the ignition lock.
X Vehicles with KEYLESS-GO start-function
or KEYLESS-GO: open the driver's door.
The vehicle electronics now have status 0.
This is the same as the key having been
removed.
X Vehicles with KEYLESS-GO start function
or KEYLESS-GO: remove the Start/Stop but-
ton from the ignition lock (Y page 133).
X If included in the vehicle equipment, remove
the tyre-change tool kit from the vehicle.
X Safeguard the vehicle against rolling away.
i Apart from some country-specific variants,
vehicles are not equipped with tyre-changing
tools. Some tools for changing a tyre are spe- cific to the vehicle. For more information on
which tools are required to perform a wheel
change on your vehicle, consult a qualified
specialist workshop.
Necessary tyre-changing tools may include,
for example:
R Jack
R wheel chock
R Wheel wrench
R Centring pin Changing a wheel
351Wheels and tyres Z