MERCEDES-BENZ ML320 1997 Complete Repair Manual

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Tow in g a t r ai le r
There are many different laws, including speed limit
restrictions, having to do with trailer towing. Make sure
t ha t your rig will be lega l, not only for w here 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.

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At very steep inclines, not manageable with selector
lever in position “1”, switch transfer case to LOW
RANGE, see page 209 for instructions on how to engage
LOW RANGE.
When going down a long hill, shift into a lower gear and
use the engine’s braking effect. Avoid riding the brakes,
thus overheating the vehicle and trailer brakes.
If the engine coolant rises to an extremely high
temperature (coolant temperature needle approaching
the red zone) when the air conditioner is on, turn off the
air conditioner. Engine coolant heat can be additionally
vented by opening the windows, switching the climate
control fan speed to high and setting the temperature
control to the maximum hot position.
Extreme care must be exercised since your vehicle with
a trailer will require additional passing distance ahead
than when driving without a trailer. Because your
vehicle and trailer is longer than your vehicle alone, you
will also need to go much farther ahead of the passed
vehicle before you can return to your lane. Parking
Wa r n i n g !
To reduce the risk of personal injury, or damage to
the vehicle powertrain, as a result of vehicle/trailer
movement, always:1. Keep right foot on brake pedal.2. Shift gear selector lever to position “N”.3. Have a second person place wheel chocks on
downhill side of left and right trailer wheels.4. Slowly release brake pedal and let vehicle and trailer roll into chocks until stopped.5. Firmly depress parking brake pedal.6. Move gear selector lever to position “P”.7. On inclines turn front wheels towards the road curb.

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Cruise control
The cruise control allows you to drive in a more relaxed
manner, for example over long distances, as it
automatically maintains the set speed by actively
regulating the throttle setting.
Any given speed above approximately 25 mph
(40 km / h) can be maintained with the cruise control by
operating the lever. 1
Accelerate and set:
Lift lever briefly to set speed.
Hold lever up to accelerate.
2 Decelerate and set:
Depress lever briefly to set speed.
Hold lever down to decelerate.
Normally the vehicle is accelerated to the desired
speed with the accelerator.
Speed is set by briefly pushing the lever to
position 1 or 2. The accelerator can then be
released.
The speed can be increased (e.g. for passing) by
using the accelerator. After the accelerator is
released, the previously set speed will be resumed
automatically.
If a set speed is to be increased or decreased
slightly, e.g. to adapt to the traffic f low, hold lever in
position 1 or 2 until the desired speed is reached, or
briefly tip the lever in the appropriate direction for
increases or decreases in 0.6 mph (1 km / h)
increments. When the lever is released, the newly
set speed remains.
1
4
2
3

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3
Canceling
To cancel the cruise control, briefly push lever to
position 3.
When you step on the brake pedal or the vehicle
speed drops below approximately 25 mph
(40 km / h), for example when driving upgrade, the
cruise control will be canceled.
If the cruise control cancels by itself and remains
inoperative until the engine is restarted, have the
system checked at your authorized Mercedes-Benz
Light Truck Center as soon as possible.
4 Resume
If the lever is briefly pushed to position 4 when
driving at a speed exceeding approximately 25 mph
(40 km / h), the vehicle resumes the speed which
was set prior to the cancellation of the cruise
control. The last memorized speed is canceled when
the key in the steering lock is turned to position 1
or 0. Important!
Moving gear selector lever to position “N” switches the
cruise control off.
Wa r n i n g !
Only use the cruise control if the traffic and
weather conditions make it advisable to travel at a
steady speed.• The use of cruise control can be dangerous on
winding roads or in heavy traffic because
conditions do not allow safe driving at a steady
speed.
• The use of cruise control can be dangerous on slippery roads. Rapid changes in tire adhesion
can result in wheel spin and loss of control.The “Resume” function should only be operated if
the driver is fully aware of the previously set speed
and wishes to resume this particular preset speed.

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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
b ra ke pe dal to slow d own. In t his case t he 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 209.
Note:
For detailed information see trailer towing on page 190.

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Brake assist system (BAS)
The BAS is designed to maximize the vehicle’s braking
capability during emergency braking maneuvers by
having maximum power boost applied to the brakes
more quickly in emergency braking conditions than
might otherwise be afforded solely by the driver’s
braking style. This can help reduce braking distances
over what ordinary driving and braking style might do.
The BAS complements the antilock brake system (ABS).
Applying the brakes very quickly results in maximum
BAS assistance.
To receive the benefit of the system you must apply
continuous full braking power during the stopping
sequence. Do not reduce brake pedal pressure.
Once the brake pedal is released, the BAS is deactivated.
The malfunction indicator lamp for the electronic
stability program (ESP) is combined with the BAS
malfunction indicator lamp.
Wa r n i n g !
BAS cannot prevent the natural laws of physics
from acting on the vehicle, nor can it increase
braking efficiency beyond that afforded by the
condition of the vehicle brakes and tires or the
traction afforded. The BAS cannot prevent
accidents, including those resulting from excessive
speed in turns, following another vehicle too
closely, or aquaplaning. Only a safe, attentive, and
skillful driver can prevent accidents. The
capabilities of a BAS equipped vehicle must never
be exploited in a reckless or dangerous manner
which could jeopardize the user’s safety or the
safety of others.

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The BAS / ESP malfunction indicator lamp in the
instrument cluster comes on with the key in steering
lock position 2 and should go out with the engine
running.
If the BAS / ESP malfunction indicator lamp comes on
permanently while the engine is running, a malfunction
has been detected in either system. As a result, it is
possible that now only partial engine output will be
available. If the BAS malfunctions, the brake system
functions in the usual manner, but without BAS. If the charging voltage falls below 10 volts, the
malfunction indicator lamp comes on and the BAS and
the ESP are switched off. When the voltage is above this
value again, the malfunction indicator lamp should go
out and the BAS is operational.
With the ABS malfunctioning, the BAS is also switched
off. Both malfunction indicator lamps come on with the
engine running.
If the BAS / ESP malfunction indicator lamp stays
illuminated, have the BAS or ESP checked at your
authorized Mercedes-Benz Light Truck Center as soon
as possible.

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Antilock brake system (ABS)
Important!
The ABS improves steering control of the vehicle during
hard braking maneuvers.
The ABS prevents the wheels from locking up above a
vehicle speed of approximately 5 mph (8 km / h)
independent of road surface conditions.
At the instant one of the wheels is about to lock up, a
slight pulsation can be felt in the brake pedal,
indicating that the ABS is in the regulating mode. Keep
firm and steady pressure on the brake pedal while
experiencing the pulsation.
Continuous steady brake pedal pressure results in
applying the advantages of the ABS, namely braking
power and ability to steer the vehicle. In the case of an emergency brake maneuver keep
continuous full pressure on the brake pedal. In this
manner only can the ABS be most effective.
On slippery road surfaces, the ABS will respond even
with light brake pedal pressure because of the
increased likelihood of locking wheels. The pulsating
brake pedal can be an indication of hazardous road
conditions and functions as a reminder to take extra
care while driving.
ABS control
The ABS malfunction indicator lamp - in the
instrument cluster comes on with the key in steering
lock position 2 and should go out with the engine
running.
When the ABS malfunction indicator lamp - in the
instrument cluster comes on while the engine is
running, it indicates that the ABS has detected a
malfunction and has switched off. In this case, the brake
system functions in the usual manner, but without
antilock assistance.
With the ABS malfunctioning, the BAS, EBP, ESP and
4-ETS+ are also switched off. The malfunction indicator
lamps come on with the engine running.
Wa r n i n g !
Do not pump the brake pedal, rather use firm,
steady brake pedal pressure. Pumping the brake
pedal defeats the purpose for ABS and significantly
reduces braking effectiveness.

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If the charging voltage falls below 10 volts, the
malfunction indicator lamp comes on and the ABS is
switched off. When the voltage is above this value again,
the malfunction indicator lamp should go out and the
ABS is operational.
If the ABS malfunction indicator lamp stays illuminated,
have the system checked at your authorized
Mercedes-Benz Light Truck Center as soon as possible. Notes:
To alert following vehicles to slippery road conditions
you discover, operate your hazard warning flashers as
appropriate.
Operating the vehicle on a single axle dynamometer
should only be done for briefly testing the brakes. To do
so, move selector lever to position “N”. The engine must
be shut off (key in steering lock position 0 or 1).
LOW RANGE – ABS
During off-road driving a special low range system for
the antilock brake system (ABS) is operational with
transmission in LOW RANGE mode, see page 211.
When applying the service brakes at speeds below
approximately 18 mph (30 km / h), the front wheels are
locked cyclically to shorten the braking distance (dig in
effect). This affects steering the vehicle.
Wa r n i n g !
ABS cannot prevent the natural laws of physics
from acting on the vehicle, nor can it increase
braking or steering efficiency beyond that afforded
by the condition of the vehicle brakes and tires or
the traction afforded. The ABS cannot prevent
accidents, including those resulting from excessive
speed in turns, following another vehicle too
closely, or aquaplaning. Only a safe, attentive, and
skillful driver can prevent accidents. The
capabilities of an ABS equipped vehicle must never
be exploited in a reckless or dangerous manner
which could jeopardize the user’s safety or the
safety of others.

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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 lamp v 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 4-ETS+ warning lamp v, 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 lamp v 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 lamp v 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 255), 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.