2015 MERCEDES-BENZ G-CLASS SUV ECU

Towing a trailer
Notes on towing a trailer
Important safety notes
GWARNING
If you rest your foot on the brake pedal while
driving, the braking system can overheat. This increases the stopping distance and can even
cause the braking system to fail. There is a
risk of an accident.
Never use the brake pedal as a footrest. Never
depress the brake pedal and the accelerator
pedal at the same time.
GWARNING
When the vehicle/trailer combination begins
to lurch, you could lose control of it. The vehi- cle/trailer combination could even rollover.
There is a risk of an accident.
On no account should you attempt to
straighten up the vehicle/trailer combination
by increasing the speed. Reduce vehicle
speed and do not countersteer. Apply the
brake as necessary.
GWARNING
If you install a ball coupling other than the one
delivered with the vehicle, the trailer tow hitch and the rear axle may be overloaded. This
applies especially if the ball coupling in ques- tion is longer or angled differently. This could seriously impair the driving characteristics
and the trailer can come loose. There is a risk
of an accident.
Only install the ball coupling delivered with
the vehicle or a ball coupling that is designed
to meet your trailer towing requirements. Do
not modify the ball coupling or the trailer tow hitch.
GWARNING
If the ball coupling is not installed correctly or not secured with the bolt provided and the
corresponding spring cotter, the trailer may
come loose. There is a risk of an accident.
Always install and secure the ball coupling asdescribed. Before every journey, ensure that
the ball coupling is secured with the bolt and
the corresponding spring cotter.
Please observe the manufacturer's operating instructions for the trailer coupling if a
detachable trailer coupling is used.
Exceeding the maximum permissible nose-
weight may cause damage to the following: R your vehicle
R the trailer
R the ball coupling
R trailer tow hitch
The vehicle/trailer combination could
become unstable.
If the noseweight used is lower than the min- imum permissible noseweight, the vehicle/
trailer combination could also become unsta-ble.
To avoid hazardous situations:
R make sure to check the noseweight before
each journey
R use a drawbar noseweight as close as pos-
sible to the maximum noseweight
R do not exceed the maximum permissible
noseweight
R do not use a noseweight lower than the
minimum permissible trailer drawbar nose-
weight
When backing up the vehicle towards the
trailer, make sure there is nobody between
the trailer and the vehicle.
The applicable permissible values, which
must not be exceeded, can be found:
R in your vehicle documents
R on the type plate of the trailer tow hitch and
trailer
R on the vehicle identification plate
Couple and uncouple the trailer carefully. If
you do not couple the trailer to the towing
vehicle correctly, the trailer could become
detached.
Towing a trailer137
Driving an d parking
Z

Driving tips
If the trailer swings from side to side:
X Do not accelerate.
X Do not counter-steer.
X Brake if necessary.
R Maintain a greater distance from the vehi-
cle in front than when driving without a
trailer.
R Avoid braking abruptly. If possible, brake
gently at first to allow the trailer to run on.
Then, increase the braking force rapidly.
R The values given for gradient-climbing
capabilities from a standstill refer to sea
level. When driving in mountainous areas,
note that the power output of the engine
and, consequently, the vehicle's gradient-
climbing capability, decreases with
increasing altitude.
Assembling the ball coupling
Assembling the ball coupling
GWARNING
The ball coupling can be damaged if the nut on the ball coupling is tightened using the incor- rect torque. As a result, the trailer may
detach. There is a risk of an accident.
Immediately after installing, have the tighten-
ing torque checked at a qualified specialist
workshop.
!Mercedes-Benz recommends that you
only use ball couplings tested and
approved for use on Mercedes-Benz vehi-
cles. This helps to avoid damage to the
vehicle.
Observe the manufacturer's installation
instructions if you use a ball coupling other than the one supplied.
X Screw in ball coupling :as far as it will go
through the hole of ball coupling carrier ;.
X
Slide securing bolt ?over the thread of
ball coupling =as far as it will go.
X Screw on nut Aas far as it will go.
X
Using a torque wrench, tighten nut Bwith
a torque of 516 lb-ft (700 Nm) .
X Check that thread Cprotruding below nut
B has the minimum required length of
0.32 in (8 mm).
X Check the assembled ball coupling for cor-
rect installation.
Towing a trailer139
Driving and pa rking
Z

iAlso observe the height of the trailer cou-
pling and the trailer manufacturer's instruc- tions.
iDepending on the height of the trailer
coupling, you may have to turn the ball cou-
pling 180° to install it on the ball coupling
carrier. The assembly is otherwise identi-
cal.
Installing the ball coupling
GWARNING
If the ball coupling is not installed correctly or not secured with the bolt provided and the
corresponding spring cotter, the trailer may
come loose. There is a risk of an accident.
Always install and secure the ball coupling as
described. Before every journey, ensure that
the ball coupling is secured with the bolt and
the corresponding spring cotter.
GWARNING
If the ball coupling is not correctly installed
and secured, it can come loose during the
journey and endanger other road users. There is a risk of an accident and injury.
Always install and secure the ball coupling as
described. Before every journey, ensure that
the ball coupling is secured with the bolt and
the corresponding spring cotter.
X Pull protective cap =in the direction of the
arrow, out of the ball coupling recess.
X Insert the ball coupling horizontally into ball
coupling recess ?in the direction of the
arrow until the hole in ball coupling Ais in
line with the hole in ball coupling recess B.
X
Slide bolt Cinto the hole in the ball cou-
pling recess and the ball coupling to the
stop.
140Towing a trailer
Driving an d parking

XSecure the bolt using spring cotter D.
Correctly installed and secured ball couplingX
Check the ball coupling, bolt and spring
cotter for correct installation.
Coupling up a trailer
GWARNING
If you uncouple a trailer with the overrun
brake engaged, you could trap your hand
between the vehicle and the trailer drawbar.
There is a risk of injury.
Do not uncouple a trailer if the overrun brake
is engaged.
!Do not connect the trailer's brake system
(if featured) to the hydraulic brake system
of the towing vehicle, as the latter is equip-
ped with an anti-lock brake system. Doing
so will result in a loss of function of the
brake systems of both the vehicle and the
trailer.
Observe the maximum permissible trailer
dimensions (width and length). Most U.S. states and all Canadian provinces
require by law:
R safety chains between the towing vehicle
and the trailer. The chains should be cross-
wound under the trailer drawbar. They must
be fastened to the vehicle's trailer cou-
pling, not to the bumper or the axle.
Allow for enough play in the chains to facil- itate turning tight corners.
R a separate brake system for certain types
of trailer.
R a safety switch for braked trailers. Check
the specific legal requirements applicable
to your state.
If the trailer detaches from the towing vehi-
cle, the safety switch applies the trailer's
brakes.
X Make sure that the automatic transmission
is set to position P.
X Apply the vehicle's parking brake.
X Couple up the trailer.
X Establish all electrical connections.
Towing a trailer
There are numerous legal requirements con-
cerning the towing of a trailer, e.g. speed
restrictions. Make sure that your vehicle/
trailer combination complies with the local
requirements not only in your area of resi-
dence but also at any location to which you
are traveling. The police and local authorities
can provide reliable information.
Please observe the following when towing a
trailer:
R To acquaint yourself with driving with a
trailer and with the resulting changes to
handling, you should practice cornering,
Towing a trailer141
Driving and parking
Z

stopping and backing up in a traffic-free location.
R Before driving, check:
- Trailer tow hitch
- Safety switch for braked trailers
- Safety chains
- Electrical connections
- Lights
- Wheels
R Adjust the exterior mirrors to provide an
unobstructed view of the rear section of the
trailer.
R If the trailer features electronically control-
led brakes, pull away the vehicle/trailer
combination carefully, manually brake
using the brake controller, and check the
brakes for correct function.
R Secure any objects on the trailer to prevent
the cargo from slipping when the vehicle is
in motion.
R If you couple up a trailer, regularly check
the cargo for secure fastening and make
sure that the trailer lamps and (if applica-
ble) the trailer brakes are functioning cor-rectly.
R Bear in mind that the handling will be less
stable when towing a trailer than when driv-
ing without one. Avoid sudden steeringmovements.
R The vehicle/trailer combination is heavier,
accelerates more slowly, has a decreased
gradient climbing capability and a longer
braking distance.
It is more susceptible to side winds and
requires more careful steering.
R If possible, avoid abrupt braking. Depress
the brake pedal moderately at first, so that
the trailer can activate its own brakes. Thenincrease the pressure on the brake pedal.
R If the automatic transmission continues to
shift back and forth between two gears
when driving up or downhill, restrict the
shift range. Select shift range 4, 3, 2,or1.
A lower gear and lower speed reduce the
risk of engine failure. R
When driving downhill, shift to a lower gear
to utilize the engine's braking effect.
Avoid continuous brake application as this
may overheat the vehicle brakes and, if
installed, the trailer brakes.
R If the coolant temperature increases dra-
matically while the air-conditioning system
is switched on, switch off the air-condition-
ing system.
Coolant heat can additionally be dissipated
by opening the windows and by setting the
blower fan and the interior temperature tomaximum.
R When overtaking, pay particular attention
to the extended length of your vehicle/
trailer combination.
Due to the length of your vehicle/trailer
combination, you will have to travel an addi-
tional distance beyond the vehicle you are
overtaking before returning to the previous lane.
Decoupling a trailer
!
Do not disconnect a trailer with an
engaged overrun brake. Otherwise, your
vehicle could be damaged by the rebound- ing of the overrun brake.
X Make sure that the automatic transmission
is set to position P.
X Apply the parking brake.
X Start the engine.
X Close all doors, including the rear door.
X Apply the trailer's parking brake.
X Detach the trailer cable and decouple thetrailer.
X Switch off the engine.
Permissible trailer and drawbar loads
Weight specifications
The gross trailer weight is calculated by add-
ing the weight of the trailer to the weight of
142Towing a trailer
Driving and parking

Display messagesPossible causes/consequences andMSolutions
$(USA
only)
J(Canada
only)
Check Brake Fluid
Level
There is not enough brake fluid in the brake fluid reservoir. In
addition, the $(USA only)/ J(Canada only) warning lamp
lights up in the instrument cluster and a warning tone sounds.
GWARNING
The braking effect 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 ( Ypage 110).
X Consult a qualified specialist workshop.
X Do not add brake fluid. This does not correct the malfunction.
6
SRS Malfunction
Service Required
The restraint system is faulty. The 6warning lamp also lights
up in the instrument cluster.
GWARNING
The air bags or Emergency Tensioning Devices may either be trig- gered unintentionally or, in the event of an accident, may not be
triggered.
There is an increased risk of injury.
X Visit a qualified specialist workshop.
For further information about the restraint system, see ( Y page 42).
6
FrontLeftMalfuncZ
tion Service
RequiredorFront
Right Malfunction
Service Required
The front left-hand or right-hand restraint system has malfunc-
tioned. The 6warning lamp also lights up in the instrument
cluster.
GWARNING
The air bags or Emergency Tensioning Devices may either be trig- gered unintentionally or, in the event of an accident, may not be
triggered.
There is an increased risk of injury.
X Visit a qualified specialist workshop.
152Display messages
On-board computer and displays

Engine
Display messagesPossible causes/consequences andMSolutions
?
Coolant Too Hot
Stop Vehicle
Switch Engine Off
The coolant is too hot.
A warning tone also sounds.
GWARNING
Do not drive when your engine is overheated. This can cause some
fluids which may have leaked into the engine compartment to
catch fire.
Steam from the overheated engine can also cause serious burns
which can occur just by opening the hood.
There is a risk of injury. X Pull over and stop the vehicle safely and switch off the engine,
paying attention to road and traffic conditions.
X Secure the vehicle against rolling away ( Ypage 110).
X Leave the vehicle and keep a safe distance from the vehicle until
the engine has cooled down.
X Make sure that the air supply to the engine radiator is not
blocked, e.g. by snow, slush or ice.
X Do not start the engine again until the display message goes out
and the coolant temperature is below 248 ‡ (120 †). Other-
wise, the engine could 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 248 ‡ (120 †).
The poly-V-belt may have torn.
X Pull over and stop the vehicle safely and switch off the engine,
paying attention to road and traffic conditions.
X Check the poly-V-belt.
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 not damaged:
X Wait until the display message disappears before restarting the
engine. Otherwise, the engine could be damaged.
X Pay attention to the coolant temperature display.
X Visit a qualified specialist workshop.
Display messages155
On-board computer and displays
Z

Driving systems
Display messagesPossible causes/consequences andMSolutions
TC shift condiZ
tionsnotfulfilled
Apply the brake/
parking brake
The parking brake has not been applied and the brake pedal has
not been depressed. The transfer case has canceled the gear
change process and is inNeutral. There is no connection between
the engine and the drive wheels.
X Pull over and stop the vehicle safely as soon as possible, paying
attention to road and traffic conditions.
X Depress the brake pedal and apply the parking brake.
X Shift the automatic transmission to neutral position N.
X Make sure all conditions for changing gears are met(Y page 132).
X Repeat the gearshift process.
TC malfunction
Consult workshop
aboutapplyingthe
parking brake
There is a malfunction in the transfer case.
X Do not shift the transfer case.
X When parking, secure the vehicle against rolling away (Y page 110).
X Have the vehicle checked at a qualified specialist workshop.
TC shift canceled
Reactivate
The transfer case has not performed the gear change process. XRepeat the gearshift process.
X Make sure all conditions for changing gears are met (Y page 132).
TC shift condiZ
tionsnotfulfilled
Max. speed 25 mph
You have exceeded the maximum speed for the gearshift process.
X Drive more slowly.
X Repeat the gearshift process.
TC shift condiZ
tionsnotfulfilled
SelectNEUTRALgear
You have not met one or more shift conditions.
X Shift the automatic transmission to neutral position N.
X Repeat the gearshift process.
TC shift condiZ
tionsnotfulfilled
Max. speed 40 mph
You have exceeded the maximum speed for the gearshift process.
X Drive more slowly.
X Repeat the gearshift process.
LOW RANGE
ON
The transfer case is in the LOW RANGEoff-road position.
HIGH RANGE
ON
The transfer case is in the HIGH RANGEon-road position.
156Displaymessages
On-board computer and displays