2002 MERCEDES-BENZ ML320 towing

209 Driving instructions
Te ch n i c a l
data Instruments
and controlsOperationDrivingInstrument
cluster displayPractical hints Car care Index Trailer towing
Trailer Hitches
Only install a trailer hitch receiver approved for your
vehicle. For information on availability and installation,
please see your authorized Mercedes-Benz Light Truck
Center.
The bumpers on your vehicle are not designed for use
with clamp-type hitches. Do not attach rental hitches or
other bumper-type hitches to them.
To reduce the possibility of damage, remove the hitch
ball adaptor from the receiver when not in use.Electrical connections
The vehicle is prewired to accept the seven-wire harness
included in the Mercedes-Benz approved trailer hitch
receiver kit. An additional four-pole conversion plug is
included in the Mercedes-Benz supplied trailer hitch
receiver kit. For further information, please see your
authorized Mercedes-Benz Light Truck Center.
In order to prevent possible damage to the vehicle’s
electrical system by incorrectly installing the trailer
wiring plug, we recommend having the harness
connected at an authorized Mercedes-Benz Light Truck
Center.
Wa r n i n g !
Failure to use proper equipment and driving
technique can result in a loss of vehicle control
when towing a trailer.Improper towing or failure to follow the
instructions contained in this guide can result in
serious injury. Follow the guidelines below
carefully to assure safe trailer operation.Ask your authorized Mercedes-Benz Light Truck
Center should you require an explanation of
information contained in this guide.

211 Driving instructions
Te ch n i c a l
data Instruments
and controlsOperationDrivingInstrument
cluster displayPractical hints Car care Index Checking weights of vehicle and trailer
To assure that the tow vehicle and trailer are in
compliance with the maximum permissible weight
limits, and to know the actual weights, have the loaded
rig (tow vehicle including driver, passengers and cargo,
trailer fully loaded) weighed on a commercial scale.
Check the vehicle’s front and rear Gross Axle Weight
(GAW), the GTW and TW. The values as measured must
not be exceeded, according to the weight listed under
“Vehicle and trailer weight and ratings”.
Attaching a trailer
Please observe maximum permitted trailer dimensions
(width and length).
Most states and all Canadian provinces require safety
chains between your tow vehicle and the trailer. The
chains should be crisscrossed under the trailer tongue.
They must be attached to the hitch receiver, and not to
the vehicle’s bumper or axle. Be sure to leave enough
slack in the chains to permit turning corners.
Most states and all Canadian provinces require a
separate brake system at various trailer weights.Caution!
Do not connect a trailer brake system (if trailer is so
equipped) directly to the vehicle’s hydraulic brake
system, as your vehicle is equipped with antilock
brakes. If you do, neither the vehicle’s brakes nor the
trailer’s brakes will function properly.
The provided vehicle electrical wiring harness for trailer
towing has a brake signal wire (color orange) for
hook-up to a brake controller.
Most states and all Canadian provinces require a
break-away switch on trailers with a separate brake
system. The switch activates the trailer brakes in the
possible event that the trailer might separate from the
tow vehicle.
You should consider using a trailer sway control system.
For further information see your authorized
Mercedes-Benz Light Truck Center.

212 Driving instructions
Te ch n i c a l
data Instruments
and controlsOperationDrivingInstrument
cluster displayPractical hints Car care Index
Towing a trailer
There are many different laws, including speed limit
restrictions, having to do with trailer towing. Make sure
that your rig will be legal, not only for where you reside,
but also for where you will be driving. A good source for
this information can be the police or local authorities.
Before you start driving with the trailer, check the
trailer hitch, break-away switch, safety chains, electrical
connections, lighting and tires. Also adjust the mirrors
to permit unobstructed view beyond rear of trailer.
If the trailer has electric brakes, start your vehicle and
trailer moving slowly, and then apply only the trailer
brake controller by hand to be sure the brakes are
working properly.
When towing a trailer, check occasionally to be sure that
the load is secure, and that lighting and trailer brakes
(if so equipped) are functioning properly.
Always secure items in the trailer to prevent load shifts
while driving.
Take into consideration that when towing a trailer, the
handling characteristics are different and less stable
from those when operating the vehicle without a trailer.
It is important to avoid sudden maneuvers.The vehicle and trailer combination is heavier, and
therefore is limited in acceleration and climbing ability,
and requires longer stopping distances. It is more prone
to reacting to side wind gusts, and requires more
sensitive steering input.
In order to gain skill and an understanding of the
vehicle’s behavior, you should practice turning,
stopping and backing up in an area which is free from
traffic.
If possible, do not brake abruptly, but rather engage the
brake slightly at first to permit the trailer to activate its
brake. Then increase the braking force.
Caution!
If the trailer should begin to sway, reduce the vehicle’s
speed and use the brake controller by hand to straighten
out the vehicle and trailer. In no case should you
attempt to straighten out the tow vehicle and trailer by
increasing the speed or oversteering and stepping on
the brakes.
If the transmission hunts between gears on inclines,
manually shift to a lower gear (select “4”, “3”, “2”
or “1”). A lower gear and reduction of speed reduces the
chance of engine overloading and / or overheating.

216 Driving systems
Te ch n i c a l
data Instruments
and controlsOperationDrivingInstrument
cluster displayPractical hints Car care Index
Notes:
If the engine does not brake the vehicle sufficiently
while driving on a downgrade, the speed you set on the
cruise control may be exceeded. In this case the
automatic transmission shifts down (max. to 3rd gear)
to maintain the set cruise control speed by using the
engine’s braking power.
As soon as the grade eases, the automatic transmission
shifts up again dependent on the selector lever position.
Nevertheless, in some cases you may have to step on the
brake pedal to slow down. In this case the cruise control
is switched off.
Use the lever to resume the previously set speed.Transmission in LOW RANGE mode
The cruise control should not be activated during off-
road driving in the LOW RANGE mode. Doing so could
reduce driving comfort.
Trailer operation
When towing a trailer, do not allow engine speed to drop
too low on inclines. Select a lower range (“3”, “2” or “1”)
in time, depending on the degree of the incline. This is
also valid with cruise control activated.
At extreme inclines switch to LOW RANGE mode, see
page 227.
Note:
For detailed information see trailer towing on page 209.

221 Driving systems
Te ch n i c a l
data Instruments
and controlsOperationDrivingInstrument
cluster displayPractical hints Car care Index Four-wheel electronic traction system (4-ETS+)
With the key in steering lock position 2, the yellow
4-ETS+ malfunction indicator lamp{ and the 4-ETS+
warning lampv come on and should go out when
the engine is running.
The 4-ETS+ improves vehicle’s ability to utilize available
traction, especially under slippery road conditions. The
brakes are applied to the spinning wheel and power is
transferred to the wheel(s) with traction.
The traction control engages at vehicle speeds up to
approx. 24 mph (40 km / h), and switches off at
50 mph (80 km / h).
The 4-ETS+ warning lampv, located in the
speedometer dial, starts to flash at any vehicle speed, as
soon as the tires lose traction and the wheels begin to
spin.
Important!
If the 4-ETS+ warning lampv flashes:
•During take-off, apply as little throttle as possible.
•While driving, ease up on the accelerator.
•Adapt your speed and driving to the prevailing road
conditions.4-ETS+ Control
If the yellow 4-ETS+ malfunction indicator lamp{
comes on while the 4-ETS+ warning lampv flashes,
the electronic traction system is being switched off
temporarily to prevent overheating of the drive wheel
brakes.
If the 4-ETS+ malfunction indicator lamp{ comes on
with the engine running, a malfunction has been
detected.
Have the 4-ETS+ checked at your authorized
Mercedes-Benz Light Truck Center as soon as possible.
With the ABS malfunctioning, the 4-ETS+ is also
switched off.
Caution!
If the vehicle is towed with the front axle raised (see
towing the vehicle on page 277), or when testing the
parking brake on a brake test dynamometer, the engine
must be shut off (key in steering lock position 0 or 1).
Otherwise, the electronic traction system will
immediately be engaged and will apply the rear wheel
brakes.

223 Driving systems
Te ch n i c a l
data Instruments
and controlsOperationDrivingInstrument
cluster displayPractical hints Car care Index Electronic stability program (ESP)
The ESP enhances directional control and reduces
driving wheel spin of the vehicle under various driving
conditions.
Over-/understeering of the vehicle is counteracted by
applying brakes to the appropriate wheel to create a
countervailing vehicle movement. Engine torque is also
limited. The ESP warning lamp, located in the
speedometer dial, starts to flash when ESP is in
operation.Important!
If the ESP warning lampv flashes:
•During take-off apply as little throttle as possible.
•While driving ease up on the accelerator.
•Adapt your speed and driving to the prevailing road
conditions.
•Do not switch off the ESP.
Caution!
If the vehicle is towed with the front axle raised (see
towing the vehicle on page 277), the engine must be
shut off (key in steering lock position 0 or 1). Otherwise,
the ESP will immediately be engaged and will apply the
rear wheel brakes.
Notes:
The malfunction indicator lamp for the ESP is combined
with that of the BAS.
The yellow BAS / ESP malfunction indicator lamp¿
in the instrument cluster and the yellow ESP warning
lampv in the speedometer dial come on with the
key in steering lock position 2. They should go out with
the engine running.
Wa r n i n g !
ESP cannot prevent the natural laws of physics
from acting on the vehicle, nor can it increase the
traction afforded. The ESP cannot prevent
accidents, including those resulting from excessive
speed in turns, or aquaplaning. Only a safe,
attentive, and skillful driver can prevent accidents.
The capabilities of an ESP equipped vehicle must
never be exploited in a reckless or dangerous
manner which could jeopardize the user’s safety or
the safety of others.

227 Driving systems
Te ch n i c a l
data Instruments
and controlsOperationDrivingInstrument
cluster displayPractical hints Car care Index Transmission control – LOW RANGE mode
The switch is located in the instrument panel.
Important!
When switching to or from the LOW RANGE mode,
observe the following:
•The vehicle must be at a complete standstill.
•The engine speed must not exceed 1500 rpm.Failure to do so may result in transmission / engine
damage not covered by the Mercedes-Benz Limited
Warranty
The LOW RANGE mode should be switched on:
•during off-road driving,
•when crossing waters,
•when towing up or down on steep gradients,
or additional practical hints refer to off-road driving
on page 202.
Important!
Operating the vehicle on a single axle dynamometer
should only be done for briefly testing the brakes. To do
so, turn key in steering lock to position 1.

231 Parking system
Te ch n i c a l
data Instruments
and controlsOperationDrivingInstrument
cluster displayPractical hints Car care Index Sensors
1Sensors located in bumper
(front bumper shown)A total of 10 sensors (1) monitor the vehicle’s front and
rear areas. Six sensors are located in the front bumper,
four sensors in the rear bumper.
For proper operation of the Parktronic always keep the
sensors clean, especially at times of snow and ice.
See page 301 for instructions on cleaning the sensors in
the bumpers.
Note:
The rear Parktronic sensors will not automatically
disengage when towing a trailer, therefore switch the
Parktronic system off, see page 234.
Switch the Parktronic system on again when no longer
towing a trailer.
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