check engine light MERCEDES-BENZ R320 2008 W251 Owner's Manual

60 Getting started
Driving
Switching on windshield wipers
Turn the combination switch to the
desired position depending on the
intensity of the rain.
MWindshield wipers off
USlow intermittent wiping
Rain sensor operation with low
sensitivity.
VFast intermittent wiping
Rain sensor operation with high
sensitivity.
uSlow continuous wiping
tFast continuous wipingIntermittent wiping
Only switch on intermittent wiping under
wet weather conditions or in the presence
of precipitation.
When you select intermittent wiping, the
rain sensor is activated. The rain sensor
automatically sets a suitable wiping
interval depending on the wetness of the
sensor surface.
Turn the combination switch to
positionU orV.
!Do not operate the windshield wipers when
the windshield is dry. Dust that accumulates on
a windshield might scratch the glass and/or
damage the wiper blades when wiping occurs on
a dry windshield. If it is necessary to operate the
windshield wipers in dry weather conditions,
always operate the windshield wipers with
windshield washer fluid (
page 61).
!If anything blocks the windshield wipers
(leaves, snow, etc.), switch them off
immediately.

For safety reasons, stop the vehicle in a safe
location and

remove the SmartKey from the starter
switch
or

turn off the engine by pressing the
KEYLESS-GO* start/stop button and
open the driver’s door (with the driver’s
door open, starter switch is in
position0, same as with SmartKey
removed from starter switch)
before attempting to remove any blockage.

Remove blockage.

Turn the windshield wipers on again.If the windshield wipers fail to function at all in
combination switch positionU orV,

set the combination switch to the next
higher wiper speed

have the windshield wipers checked at the
nearest authorized Mercedes-Benz Light
Truck Center
!Do not leave windshield wipers on an
intermittent setting when the vehicle is taken
to an automatic car wash or during windshield
cleaning. Windshield wipers will operate in the
presence of water sprayed on the windshield,
and windshield wipers may be damaged as a
result.
!If you have set intermittent wiping, dirt on
the surface of the rain sensor or optical effects
may cause the windshield wipers to wipe in an
undesired fashion. This could then damage the
windshield wiper blades or scratch the wind-
shield. You should therefore switch off the wind-
shield wipers when weather conditions are dry.

63 Getting started
Driving
The coolant temperature is above
248°F (120°C)
The coolant is too hot and is no longer
cooling the engine.
Stop the vehicle in a safe location as
soon as possible and turn off the
engine. Allow engine and coolant to
cool.
Check the coolant level and add
coolant if necessary (
page 360).In case of accident
If the vehicle is leaking fuel:
Do not start the engine under any
circumstances.
Notify local fire and/or police authori-
ties.
If the extent of the damage cannot be
determined:
Contact an authorized Mercedes-Benz
Light Truck Center or call Roadside
Assistance.
If no damage can be determined on the

major assemblies

fuel system

engine mount:
Start the engine in the usual manner.

194 Controls in detail
Automatic transmission
Transmission positions
The current transmission position appears
in the multifunction display.
1Current transmission position
!If the current transmission position does not
appear in the multifunction display due to a
malfunction, for example, make sure that the
automatic transmission is in the desired position
by carefully driving off with the transmission in
drive positionD and program modeS
(
page 200) selected. Do not limit the gear
range.
Effect
ìPark position
Shift into park positionP only
when vehicle is stopped. The
park position is not intended to
serve as a brake when the vehi-
cle is parked. Rather, the driver
should always set the parking
brake in addition to shifting into
park positionP to secure the
vehicle.
If the vehicle’s electrical system
is malfunctioning, the automatic
transmission could remain
locked in park positionP.
Have the vehicle checked as
soon as possible by an autho-
rized Mercedes-Benz Light
Truck Center.
!SmartKey:
If you turn off the engine using the SmartKey and

remove the SmartKey from the starter
switch
or

open a front door
the transmission will shift to park positionP
automatically.
Keep in mind that turning off the engine with the
SmartKey alone only will automatically shift the
transmission to neutral positionN.
!KEYLESS-GO*:
If you turn off the engine using the KEYLESS-GO
start/stop button and open a front door, the
transmission will shift to park positionP
automatically.
Keep in mind that turning off the engine using
the KEYLESS-GO start/stop button alone only
will automatically shift the transmission to
neutral positionN.

202 Controls in detail
Automatic transmission
Extending gear range
Briefly press right shift button2.
The transmission will shift to the next
higher gear as permitted by the shift
program. This action simultaneously
extends the gear range of the transmis-
sion.Canceling gear range limitPress and hold right shift button2
until the cipher for the current gear
range disappears from the multifunc-
tion display (
page 199).
The transmission will shift from the
current gear range directly to gear
rangeD.
Shifting into optimal gear range
Press and hold left shift button1.
The transmission will automatically
select the gear range suited for optimal
acceleration and deceleration. This will
involve shifting down one or more
gears.Emergency operation (Limp-Home
Mode)
If vehicle acceleration becomes less re-
sponsive or sluggish or the transmission
no longer shifts, the transmission is most
likely operating in limp-home (emergency
operation) mode. In this mode only second
gear and reverse gear can be selected.
Stop the vehicle in a safe location.
Shift to park positionP.
Turn off the engine.
Wait at least 10 seconds before
restarting.
Restart the engine.
Shift to drive positionD (for second
gear) or reverse gearR.
Have the transmission checked at an
authorized Mercedes-Benz Light Truck
Center as soon as possible.
iIf you press on the accelerator when the en-
gine has reached its rpm limit, the transmission
will upshift beyond any gear range limit selected.

219 Controls in detail
Climate control
Air conditioning
The air conditioning is operational while
the engine is running and cools the interior
air to the temperature set by the operator.
In addition, the air conditioning dehumidi-
fies the interior air at outside temperatures
above 41°F (5° C) and helps prevent
window fogging.
Deactivating
It is possible to deactivate the air condi-
tioning (cooling) function of the climate
control system. The air in the vehicle will
then no longer be cooled or dehumidified.Press button9 (page 210).
The indicator lamp on the button goes
out.
Activating
Moist air can fog up the windows. You can
dehumidify the air with the air condition-
ing.
Press button9 (page 210) again.
The indicator lamp on the button
comes on.
The air conditioning uses the refrigerant
R134a. This refrigerant is free of CFCs
which are harmful to the ozone layer.
Residual heat and ventilation
With the engine switched off, it is possible
to continue to heat or ventilate the interior
for up to 30 minutes. This feature makes
use of the residual heat produced by the
engine.
Activating
Switch off the ignition (page 39).
Press button9 (page 210).
The indicator lamp on the button
comes on.
iCondensation may drip out from underneath
the vehicle. This is normal and not an indication
of a malfunction.
Warning!G
If you turn off the cooling function, the inte-
rior air is not dried. The windows can fog up
more quickly. Window fogging may impair
visibility and endanger you and others.
!If the air conditioning cannot be turned on
again, this indicates that the air conditioning is
losing refrigerant. The compressor has turned
off.
Have the air conditioning checked at the nearest
authorized Mercedes-Benz Light Truck Center.
iHow long the system will provide heating
depends on

the coolant temperature

the battery voltage
Regardless of the temperature and air volume
set on the climate control panel, an interior tem-
perature is aimed at by 72°F (22°C) and the
blower runs on low speed to protect the vehicle
battery.

341 Operation
Driving instructions
To help prevent brake disk corrosion after
driving on wet road surfaces (particularly
salted roads), it is advisable to brake the
vehicle with considerable force prior to
parking. The heat generated serves to dry
the brakes.
If your brake system is normally only
subjected to moderate loads, you should
occasionally test the effectiveness of the
brakes by applying above-normal braking
pressure at higher speeds. This will also
enhance the grip of the brake pads.Refer to the description of the Brake Assist
System (BAS) (
page 101).
Brake pad wear or a leak in the system may
be the reason for low brake fluid level in
the reservoir.
The brake fluid level in the reservoir may
be too low if the brake warning lamp
in the instrument cluster comes on and an
acoustic warning sounds although the
parking brake is released (
page 415).
Observe additional messages in the multi-
function display that may appear
(
page 447).
Have the brake system inspected
immediately. Contact an authorized
Mercedes-Benz Light Truck Center.All checks and service work on the brake
system should be carried out by qualified
technicians only. Contact an authorized
Mercedes-Benz Light Truck Center.
Only install brake pads and brake fluid
recommended by Mercedes-Benz.
!Vehicles with 4MATIC:
Because the ESP® operates automatically, the
engine and ignition must be shut off (SmartKey
in starter switch position0 or1 or KEYLESS-GO*
start/stop button in position0or1) when test-
ing the parking brake on a brake test dynamom-
eter and such testing should be no longer than
10 seconds.
Active braking action through the ESP
® may
otherwise seriously damage the brake system
which is not covered by the Mercedes-Benz
Limited Warranty.
Warning!G
Make sure not to endanger any other road
users when carrying out these braking
maneuvers.
Warning!G
If other than recommended brake pads are
installed, or other than recommended brake
fluid is used, the braking properties of the
vehicle can be degraded to an extent that
safe braking is substantially impaired. This
could result in an accident.

355 Operation
At the gas station
Engine oil level
For more information on engine oil, see
“Engine oil” (
page 358).
Coolant
For normal replenishing, use water (pota-
ble water quality). For more information,
see “Coolant level” (
page 360) and
“Fuels, coolants, lubricants, etc.”
(
page 536).
Brake fluidWindshield/rear window washer
system and headlamp cleaning
system*
For more information on refilling the wash-
er reservoir, see “Windshield/rear window
washer system and headlamp cleaning
system*” (
page 362).
Vehicle lighting
Check function and cleanliness. For infor-
mation on replacing light bulbs, see “Re-
placing bulbs” (
page 480).
For more information, see “Exterior lamp
switch” (
page 143).
Tire inflation pressure
For more information, see “Checking tire
inflation pressure” (
page 373).
!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 immediately. Contact an
authorized Mercedes-Benz Light Truck Center
immediately. Do not add brake fluid as this will
not solve the problem. For more information, see
“Brake fluid” (
page 539).

358 Operation
Engine compartment
Closing
Let 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.
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 R 350 4MATIC
1Oil dipstick
2Upper mark
3Lower mark
Open the hood (page 356).
Pull out oil dipstick1.
Warning!G
When closing the hood, use extreme caution
not to catch hand or fingers. Be careful that
you do not close the hood on anyone.
Make sure the hood is securely engaged be-
fore driving. Do not continue driving if the
hood can no longer engage after an accident
for example. The hood could otherwise
come loose while the vehicle is in motion
and injure you and/or others.
!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.

360 Operation
Engine compartment
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 536) and
(
page 538).
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. To check
the coolant level, the vehicle must be
parked on level ground.
!Excess oil must be siphoned or drained off.
It could cause damage to the engine or
emission control system not covered by the
Mercedes-Benz Limited Warranty.
Warning!G
In order to avoid any potentially serious
burns:

Use extreme caution when opening the
hood if there are any signs of steam or
coolant leaking from the cooling system,
or if the coolant temperature display
indicates that the coolant is overheated.

Do not remove pressure cap on coolant
reservoir if coolant temperature is
above 158°F (70°C). Allow engine to
cool down before removing cap. The
coolant reservoir contains hot fluid and
is under pressure.

Using a rag, slowly open the cap approx-
imately 1/2turn to relieve excess pres-
sure. If opened immediately, scalding


398 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 544).

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.
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 M+S and
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 winter
tires mounted 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 at your tire
dealer or 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.