2008 MERCEDES-BENZ GL450 check engine light

368 Operation
Driving instructions

Always secure items in the trailer to
prevent load shifts while driving.

When towing a trailer, check occasion-
ally to make sure the load is secure,
and that lighting and trailer brakes (if
so equipped) are functioning properly.

Take into consideration that when tow-
ing a trailer, the handling characteris-
tics are different and less stable from
those when operating the vehicle with-
out a trailer.
It is important to avoid sudden maneu-
vers.

The vehicle and trailer combination is
heavier, and therefore is limited in ac-
celeration and climbing ability, and re-
quires longer stopping distances.
It is more prone to reacting to cross
wind gusts, and requires more sensi-
tive steering input.

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.

If the transmission repeatedly shifts
between gears on inclines, manually
shift to a lower gear (select 4, 3, 2 or 1)
(
page 197).
A lower gear and reduction of speed re-
duces the chance of engine overload-
ing and/or overheating.

On very steep inclines, not manageable
with automatic transmission in1,
switch on off-road driving program
(
page 278) or LOW RANGE mode*
(
page 201).

When going down a long hill, shift into
a lower gear and use the engine’s brak-
ing effect.
Avoid riding the brakes, thus overheat-
ing the vehicle and trailer brakes.

If the engine coolant rises to an ex-
tremely high temperature (coolant tem-
perature needle approaching the red
zone) when the air conditioning is on,
turn off the air conditioning system.
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 re-
turn to your lane.
!If the trailer should begin to sway, reduce
the vehicle’s speed immediately.
In no case attempt to straighten out the tow
vehicle and trailer by increasing the speed.
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379 Operation
Engine compartment
The hood lock release lever is located in
the driver’s footwell.
1Release lever
Pull release lever1 downwards.
The hood is unlocked. Handle2 pro-
trudes slightly from the radiator grille.
If not, lift the hood slightly.2Handle for opening the hood
Press and hold handle2.
The hood is unlocked.
Pull up on the hood in direction of ar-
row and then release it.
The hood will be automatically held
open at shoulder height by gas-filled
struts.ClosingLet the hood drop from a height of
approximately 1 ft (30 cm).
The hood will lock audibly.
Check to make sure the hood is fully
closed.
If you can raise the hood at a point
above the headlamps, then it is not
properly closed. Open it again and let it
drop with somewhat greater force.

with the engine running

while starting the engine

when the ignition is switched on
!To avoid damage to the windshield wipers or
hood, never open the hood if the wiper arms are
folded forward away from the windshield.
Warning!G
When closing the hood, use extreme caution
not to catch hands or fingers. Be careful that
you do not close the hood on anyone.
Make sure that the hood is securely en-
gaged before driving off. Do not continue
driving if the hood can no longer engage af-
ter an accident, for example. The hood could
otherwise come loose while the vehicle is in
motion and endanger you and others.
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380 Operation
Engine compartment
Engine oil
The amount of oil your engine needs will
depend on a number of factors, including
driving style. Increased oil consumption
can occur when

the vehicle is new

the vehicle is driven frequently at
higher engine speeds
Engine oil consumption checks should only
be made after the vehicle break-in period.Checking engine oil level
When checking the oil level

the vehicle must be parked on level
ground

the vehicle must have been stationary
for at least 5 minutes with the engine
turned off
Example illustration GL 450 (GL 320 CDI,
GL 550 similar)
1Oil dipstick
2Upper mark
3Lower mark
Open the hood (page 378).
Pull out oil dipstick1.
Wipe oil dipstick1 clean.
Fully insert oil dipstick1 into the
dipstick guide tube.
Pull out oil dipstick1 again after
approximately 3 seconds to obtain
accurate reading.
The oil level is correct when it is be-
tween lower mark3 (min.) and upper
mark2 (max.) of the oil dipstick.
If necessary, add engine oil
(
page 381).
For more information on engine oil, see
“Technical data” section (
page 562) and
(
page 564).
!Do not use any special lubricant additives,
as these may damage the drive assemblies.
Using special additives not approved by
Mercedes-Benz may cause damage not covered
by the Mercedes-Benz Limited Warranty.
More information on this subject is available at
any Mercedes-Benz Light Truck Center.
iThe filling quantity between the upper and
lower marks on the oil dipstick is approximately
2.1 US qt. (2.0 l).
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381 Operation
Engine compartment
Adding engine oil
Example illustration GL 450 (GL 320 CDI,
GL 550 similar)
1Filler cap
Unscrew filler cap1 from filler neck.
Add engine oil as required. Never over-
fill with oil.
Be careful not to spill any oil when adding.
Avoid environmental damage caused by oil
entering the ground or water.
Screw filler cap1 back on filler neck.
For more information on engine oil, see
“Technical data” section (
page 562) and
(
page 564).
Transmission fluid level
The transmission fluid level does not need
to be checked. If you notice transmission
fluid loss or gear shifting malfunctions,
have an authorized Mercedes-Benz Light
Truck Center check the automatic trans-
mission.
Coolant level
The engine coolant is a mixture of water
and anticorrosion/antifreeze.
When checking the coolant level

the vehicle must be parked on level
ground

the coolant temperature must be below
158°F (70°C)
!Only use approved engine oils and oil filters
required for vehicles with Maintenance System.
For a listing of approved engine oils and oil
filters, refer to the Factory Approved Service
Products pamphlet (USA only) in your vehicle
literature portfolio, or contact an authorized
Mercedes-Benz Light Truck Center.
Using engine oils and oil filters of specification
other than those expressly required for the
Maintenance System, or changing of oil and oil
filter at change intervals longer than those called
for by the Maintenance System will result in
engine or emission control system damage not
covered by the Mercedes-Benz Limited
Warranty.
!Excess oil must be siphoned or drained off.
It could cause damage to the engine and/or
catalytic converter (gasoline engine) or the oxi-
dation catalyst (diesel engine) not covered by
the Mercedes-Benz Limited Warranty.
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420 Operation
Winter driving
Before the onset of winter, have your
vehicle winterized at an authorized
Mercedes-Benz Light Truck Center. This
service includes:

Check of anticorrosion and antifreeze
concentration.

Addition of cleaning concentrate to the
water of the windshield and headlamp
cleaning system. Add MB Concentrate
“MB SummerFit” to a premixed wind-
shield washer solvent/antifreeze
which is formulated for temperatures
below freezing point (
page 569).

Battery test. Battery capacity drops
with decreasing ambient temperature.
A well charged battery helps to make
sure that the engine can be started
even at low ambient temperatures.

Tire change. Mercedes-Benz recom-
mends M+S rated radial-ply tires with a
minimum tread depth of approximately
1/6in (4 mm) on all four wheels for the
winter season.
Winter tires
Always use winter tires at temperatures
below 45°F (7°C) and whenever wintry
road conditions prevail. Not all M+S rated
tires provide special winter performance.
Make sure the tires you use show the
mountain/snowflake.marking on the
tire sidewall. These tires meet specific
snow traction performance requirements
of the Rubber Manufacturers Association
(RMA) and The Rubber Association of Can-
ada (RAC) and have been designed specif-
ically for use in snow conditions. Use of
winter tires is the only way to achieve the
maximum effectiveness of the ABS, ESP
®,
4-ETS, and EBP in winter operation.
For safe handling, make sure all mounted
winter tires are of the same make and have
the same tread design.Always observe the speed rating of the
winter tires installed on your vehicle. If the
maximum speed for which your tires are
rated is below the speed rating of your
vehicle, you must place a notice to this
effect where it will be seen by the driver.
Such notices are available from your tire
dealer or from any authorized
Mercedes-Benz Light Truck Center.
Warning!G
Winter tires with a tread depth of less than 1/6in (4 mm) must be replaced. They are no
longer suitable for winter operation.
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424 Operation
Maintenance
Calling up the maintenance service
indicator display
You can call up the maintenance service in-
dicator display at any time to check when
the next maintenance service is due.
Switch on the ignition (page 42).
Press buttonè orÿ on the mul-
tifunction steering wheel repeatedly
until the standard display appears in
the multifunction display (
page 162).
Press buttonk orj until the
maintenance service indicator display
with the service symbol9 and the
service deadline appears in the multi-
function display.Resetting the maintenance service
indicator
In the event that the maintenance service
on your vehicle is not carried out by an
authorized Mercedes-Benz Light Truck
Center, you can have the maintenance
service indicator reset. The automotive
maintenance facility carrying out the
maintenance service will find the informa-
tion for resetting the maintenance service
indicator in the maintenance-relevant
information for your vehicle. Such informa-
tion is available from any authorized
Mercedes-Benz Light Truck Center or di-
rectly from Mercedes-Benz.
iIf the battery is disconnected, the days of
disconnection will not be included in the count
shown by the maintenance service indicator.To arrive at the true maintenance service dead-
line, you will need to subtract these days from
the days shown in the maintenance service indi-
cator message or maintenance service indicator
display.
Do not confuse the maintenance service indica-
tor with the engine oil level indicatorN.
!If the maintenance service indicator was
inadvertently reset, have an authorized
Mercedes-Benz Light Truck Center correct it.
Only reset if the proper maintenance service has
been performed. Resetting the system without
performing the proper service as called for by
the maintenance service indicator will result in
engine damage and/or other vehicle damage not
covered by the Mercedes-Benz Limited
Warranty.
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436 Practical hints
What to do if …
Lamps in instrument clusterGeneral information:
If any of the following lamps in the instru-
ment cluster fails to come on during thebulb self-check when switching on the
ignition, have the respective bulb checked
and replaced if necessary.
ProblemPossible cause/consequenceSuggested solution
-The yellow ABS indicator lamp
comes on while the engine is
running.ABS has detected a malfunction and has
switched off. The BAS, ESP®, EBP, and 4-ETS
are also switched off (see messages in multi-
function display).
The brake system is still functioning normally
but without the ABS available.
If the ABS control unit is malfunctioning,
other systems such as the navigation
system* or the automatic transmission may
also be malfunctioning.
Continue driving with added caution.
Wheels may lock during hard braking,
reducing steering capability.
Read and observe messages in the
multifunction display (
page 449).
Have the system checked at an
authorized Mercedes-Benz Light
Truck Center as soon as possible.
Failure to follow these instructions
increases the risk of an accident.
The charging voltage has fallen below
10 volts. The ABS has switched off.
The battery might not be charged sufficiently.When the voltage is above this value
again, the ABS is operational again and
the ABS indicator lamp should go out.
If the ABS indicator lamp does not go out:
Have the generator (alternator) and
the battery checked.
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437 Practical hints
What to do if …
ProblemPossible cause/conse-
quenceSuggested solution
-The yellow ABS indicator lamp comes on while
the engine is running.The self-diagnosis has not yet
been completed yet.The display will clear after driving a short
distance at a vehicle speed of above
12 mph (20 km/h).
;(USA only)
3(Canada only)
The red brake warning lamp
comes on while driving and an
acoustic warning sounds.You are driving with the
parking brake set.Release the parking brake
(
page 59).
There is insufficient brake fluid
in the reservoir.Risk of accident! Carefully stop the
vehicle in a safe location or as soon as
it is safe to do so.
Apply the parking brake (page 67).
Contact an authorized
Mercedes-Benz Light Truck Center.
Do not add brake fluid! This will not
solve the problem.
Warning!G
Driving with the brake warning lamp illumi-
nated can result in an accident. Have your
brake system checked immediately if the
brake warning lamp stays on.
Do not add brake fluid before checking the
brake system. Overfilling the brake fluid res-
ervoir can result in spilling brake fluid on hot
engine parts and the brake fluid catching
fire. You can be seriously burned.!If you find that the brake fluid in the brake
fluid reservoir has fallen to the minimum mark or
below, have the brake system checked for brake
pad thickness and leaks.
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