check engine MERCEDES-BENZ M-Class 2015 W166 Owner's Guide

Driving off-road increases the likelihood of
damage to the vehicle, which, in turn, can lead to failure of the mechanical assembly or sys-
tems. Adapt your driving style to suit the ter- rain conditions. Drive carefully. Have damage
to the vehicle rectified immediately at a quali-
fied specialist workshop.
Do not switch to transmission position N
when driving off-road. You could lose control
of the vehicle if you attempt to brake using
the service brake. If the gradient is too steep, drive backwards in reverse gear.
General notes Read this section carefully before driving your
vehicle off-road. Practice by driving over more gentle off-road terrain first.
Familiarize yourself with the characteristics
of your vehicle and the gear shift operation
before driving through difficult terrain.
The following driving systems are specially
adapted to off-road driving:
R Off-road program 1 and 2 (vehicles with the
ON&OFFROAD package) (Y page 251)
R LOW RANGE off-road gear (vehicles with
the ON&OFFROAD package)
(Y page 253)
R Differential lock (vehicles with the
ON&OFFROAD package) (Y page 252)
R Off-road ABS (Y page 68)
R Off-road 4ETS (Y page 73)
R AIRMATIC package (vehicle level)
(Y page 211)
R DSR (Downhill Speed Regulation)
(Y page 250)
Observe the following notes:
R Stop the vehicle before starting to drive
along an off-road route.
R For vehicles with the AIRMATIC pack-
age: select a vehicle level that is suitable
for the off-road terrain. To avoid damaging
the vehicle, make sure there is always suf-
ficient ground clearance. R
Check that items of luggage and loads are
stowed safely and are well secured
(Y page 339).
R Always keep the engine running and in gear
when driving on a downhill gradient. Acti-
vate DSR (Y page 250).
R Always keep the doors, tailgate, windows
and sliding sunroof closed while driving.
R Adapt your speed to the terrain. The
rougher, steeper or more ruts on the ter-
rain, the slower your speed should be.
R Drive slowly and at an even speed through
the water. Ensure that a bow wave does not
form as you drive.
R Drive with extreme care on unfamiliar off-
road routes where visibility is poor. For
safety reasons, get out of the vehicle first
and survey the off-road route.
R Look out for obstacles, such as rocks,
holes, tree stumps and furrows.
R Check the depth of water before fording
rivers and streams.
R When fording, do not stop and do not
switch off the engine.
R On sand, drive quickly to overcome the roll-
ing resistance. Otherwise the vehicle's
wheels could become stuck in loose
ground.
R Do not jump with the vehicle as this will
interrupt the vehicle's propulsion.
R Always keep the engine running and in gear
when driving on a slope.
R Do not shift the automatic transmission to
transmission position N.
i Do not use the HOLD function when driv-
ing off-road, on steep uphill or downhill gra-
dients or on slippery or loose surfaces. The HOLD function cannot hold the vehicle on
such surfaces.
Checklist before driving off-road !
If the engine oil warning lamp lights up
while the vehicle is in motion, stop the vehi-
cle in a safe place as soon as possible. 192
Driving
tipsDriving an d parking

Check the engine oil level. The engine oil
warning lamp warning must not be ignored. Continuing the journey while the symbol is
displayed could lead to engine damage.
X Engine oil level: check the engine oil level
and add oil if necessary.
When driving on steep gradients, the
engine oil level must be sufficiently high to
ensure a correct oil supply in the vehicle.
X DEF tank (BlueTEC vehicles): check the
level and top up if necessary (Y page 180).
X Tire-changing tool kit: check that the jack
is working and make sure you have the lug
wrench, a robust tow cable and a folding
spade in the vehicle.
X Wheels and tires: check the tire tread
depth and tire pressure.
X Check for damage and remove any foreign
objects, e.g. small stones, from the
wheels/tires.
X Replace any missing valve caps.
X Replace dented or damaged wheels.
X Rims: dented or bent rims can result in a
loss of tire pressure and damage the tire
bead. Therefore, check your rims before
driving off-road and replace them as
required.
Checklist after driving off-road !
If you detect damage to the vehicle after
driving off-road, have the vehicle checked
immediately at a qualified specialist work-
shop.
X Vehicles with the ON&OFFROAD pack-
age: activate the on-road program
(Y page 251).
X Deactivate the LOW RANGE off-road gear
(Y page 253).
X Deactivate DSR (Y page 250).
X Vehicles with the AIRMATIC package:
lower the vehicle to a ride height suitable
for the road conditions, e.g. to the high-
way/high-speed level. X
Clean the headlamps and rear lights and
check for damage.
X Clean the front and rear license plates.
X Clean the wheels/tires with a water jet and
remove any foreign objects.
X Clean the wheels, wheel housings and the
vehicle underside with a water jet; check
for any foreign objects and damage.
X Check whether twigs or other parts of
plants have become trapped. These
increase the risk of fire and can damage
fuel pipes, brake hoses or the rubber bel-
lows of the axle joints and propeller shafts.
X After the trip, examine without fail the
entire undercarriage, wheels, tires, brakes,
bodywork structure, steering, chassis and
exhaust system for damage.
X After driving for extended periods across
sand, mud, gravel, water or in similarly dirty
conditions, have the brake discs, wheels,
brake pads/linings and axle joints checked
and cleaned.
X If you detect strong vibrations after off-road
travel, check for foreign objects in the
wheels and drive train and remove them if
necessary. Foreign objects can disturb the
balance and cause vibrations.
Driving over rough terrain places greater
demands on your vehicle than driving on nor-
mal roads. After driving off-road, check the
vehicle. This allows you to detect damage
promptly and reduce the risk of an accident to
yourself and other road users.
Driving on sand Observe the following rules when driving on
sand:
R Vehicles with the ON&OFFROAD pack-
age: select off-road program 1
(Y page 251).
R Vehicles with the AIRMATIC package:
select a raised vehicle level.
R Avoid high engine speeds. Driving tips
193Driving and pa rking Z

R
Use the left-hand steering wheel paddle
shifter to shift to a lower gear appropriate
to the terrain.
R Drive quickly to overcome the rolling resist-
ance. Otherwise the vehicle's wheels could
become stuck in loose ground.
R Drive in the tracks of other vehicles if pos-
sible. Make sure that:
- the tire ruts are not too deep.
- the sand is sufficiently firm.
- the ground clearance of the vehicle is
sufficient.
Tire ruts and gravel roads !
Check that the ruts are not too deep and
that your vehicle has sufficient clearance.
Otherwise, your vehicle could be damaged
or bottom out and get stuck.
Observe the following rules when driving
along ruts in off-road terrain or on roads with loose gravel:
R Vehicles with the AIRMATIC package:
select a raised vehicle level.
R Avoid high engine speeds.
R Shift to a lower gear using the left-hand
steering wheel paddle shifter.
R Drive slowly.
R Where ruts are too deep, drive with the
wheels of one side on the center grassy
area, if possible.
Driving over obstacles !
Obstacles could damage the floor of the
vehicle or components of the chassis. Ask
passengers for guidance when driving over
large obstacles. The passenger should
always keep a safe distance from the vehi- cle when doing so in order to avoid injury as
a result of unexpected vehicle movements. After driving off-road or over obstacles,
check the vehicle for possible damage,
especially to the underbody and the com-
ponents of the chassis. Observe the following rules when driving over
tree stumps, large stones and other obsta-
cles:
R Select the LOW RANGE (Y page 253) off-
road gear.
R Raise the vehicle level.
R Avoid high engine speeds.
R Shift to a lower gear using the left-hand
steering wheel paddle shifter.
R Drive very slowly.
R Drive straight over the center of obstacles. Traveling uphill
Approach/departure angle G
WARNING
If you drive on a steep incline at an angle or
turn when driving on an incline, the vehicle
could slip sideways, tip and rollover. There is a risk of an accident.
Always drive on a steep incline in the line of
fall (straight up or down) and do not turn the
vehicle.
R Observe the rules on off-road driving.
R Do not drive at an angle on slopes, inclines
or gradients, but instead follow the direct
line of fall. The maximum gradient-climbing capability of your vehicle is 100%, which
corresponds to an approach/departure
angle of 45°. Note that the climbing ability
of your vehicle depends on the terrain con- ditions. 194
Driving tipsDriving and parking

R
When driving down an incline, make use of
the engine's braking effect. Observe the
engine speed; do not overrev the engine.
R Before driving on extreme uphill and down-
hill gradients, select the LOW RANGE off-
road gear (Y page 253).
R Drive slowly.
R Avoid high engine speeds. Drive at appro-
priate engine speeds (maximum
3,000 rpm).
R Use the left-hand paddle shifter to shift into
a lower gear in good time on long and steep
downhill gradients.
R Check the brakes after prolonged off-road
driving.
i Hill start assist will aid you when pulling
away on a hill.
For further information about hill start
assist, see (Y page 161).
Do not switch to transmission position N
when driving off-road. If you try to brake the
vehicle using the service brake, you could
lose control of the vehicle. If the gradient is
too steep for your vehicle, drive back down in
reverse gear.
Always observe the approach/departure
angle values (Y page 458).
Maximum gradient-climbing capability Always observe the maximum gradient climb-
ing ability values (Y page 458).
Hilltops When driving up an uphill gradient, slightly
reduce pressure on the accelerator immedi-
ately before reaching the brow of the hill. Use
the vehicle's own impetus to drive over the
top of the hill.
This style of driving prevents:
R the vehicle from lifting off the ground on the
brow of a hill
R the vehicle from traveling too quickly down
the other side Driving downhill R
Drive slowly.
R Do not drive at an angle down steep
inclines. Steer into the line of fall and drive
with the front wheels aligned straight. Oth- erwise, the vehicle could slip sideways, tip
and rollover.
R Shift to a lower gear using the left-hand
paddle shifter before tackling steep down-
hill gradients.
R Activate DSR. If this is not sufficient, brake
gently. When doing so, make sure that the
vehicle is facing in the direction of the line
of fall.
R Check that the brakes are working normally
after a long downhill stretch.
i The special off-road ABS setting enables a
precise, brief and repeated locking of the
front wheels. This causes them to dig into
loose earth. Be aware that the front wheels easily skid across the ground surface if
completely braked and therefore lose their
ability to steer. Driving systems
Cruise control
General notes Cruise control maintains a constant road
speed for you. It brakes automatically in order
to avoid exceeding the set speed. You must
select a lower gear in good time on long and
steep downhill gradients, especially if the
vehicle is laden or towing a trailer. By doing
so, you will make use of the braking effect of
the engine. This relieves the load on the brake
system and prevents the brakes from over-
heating and wearing too quickly.
Use cruise control only if road and traffic con-
ditions make it appropriate to maintain a
steady speed for a prolonged period. You can store any road speed above 20 mph
(30 km/h). Driving systems
195Driving and parking Z

sponding side lights up red. This warning is
always emitted when a vehicle enters the
blind spot monitoring range from behind or
from the side. When you overtake a vehicle,
the warning only occurs if the difference in
speed is less than 7 mph (12 km/h).
The yellow indicator lamp goes out if reverse gear is engaged. In this event, Blind Spot
Assist is no longer active.
The brightness of the indicator/warning
lamps is adjusted automatically according to
the ambient light.
Collision warning
If a vehicle is detected in the monitoring range
of Blind Spot Assist and you switch on the
corresponding turn signal, a double warning
tone sounds. Red warning lamp 0043flashes. If
the turn signal remains on, detected vehicles
are indicated by the flashing of red warning
lamp 0043. There are no further warning tones.
Switching on Blind Spot Assist
X Make sure that the radar sensor system
(Y page 279) and Blind Spot Assist
(Y page 276) are activated in the on-board
computer.
X Turn the SmartKey to position 2in the igni-
tion lock.
Warning lamps 0043in the exterior mirrors
light up red for approximately 1.5 seconds
and then turn yellow.
Towing a trailer
When you attach a trailer, make sure you have correctly established the electrical connec-
tion. This can be accomplished by checking
the trailer lighting. In this event, Blind Spot
Assist is deactivated. The indicator lamp in
the exterior mirrors lights up yellow, and the
Blind
Blind Spot SpotAssist
Assist Currently
Currently Unavail‐
Unavail‐
able See Operator's Manual
able See Operator's Manual message
appears in the multifunction display.
i You can deactivate the indicator lamps in
the exterior mirrors. To do so, switch off Blind Spot Assist when:
R the SmartKey is in position 2in the igni-
tion lock
R the engine is not running
R the electrical connection to the trailer
has been established
Lane Keeping Assist General notes
0043
Lane Keeping Assist camera
Lane Keeping Assist monitors the area in
front of your vehicle by means of a camera 0043
at the top of the windshield. Lane Keeping
Assist detects lane markings on the road and
warns you before you leave your lane unin-
tentionally.
If you select km kmon the on-board computer in
the Display Unit Speed-/Odometer
Display Unit Speed-/Odometer func-
tion (Y page 277), Lane Keeping Assist is
active starting at a speed of 60 km/h. If the
miles miles display unit is selected, the assistance
range begins at 40 mph.
A warning may be given if a front wheel
passes over a lane marking. It will warn you by means of intermittent vibration in the steer-
ing wheel for up to 1.5 seconds.
Important safety notes G
WARNING
Lane Keeping Assist may not always clearly
recognize lane markings. Driving systems
239Driving and parking
Z

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.
X Make sure that the automatic transmission
is set to position P.
X Apply the vehicle's electric parking brake.
X Start the engine.
X Vehicles with the AIRMATIC package:
select highway level.
X Vehicles with ADS: set ADS toAUTOor
COMF.
X Switch off the engine.
X Close all doors and the tailgate.
X Couple up the trailer.
X Establish all electrical connections.
X Check that the trailer lighting system is
working.
i Vehicles with the AIRMATIC package:
with a trailer attached, the vehicle will
always remain at highway level. When cou-
pling up a trailer, please observe the fol-
lowing:
R Unless highway level has been set man-
ually, the vehicle is automatically low-
ered to highway level. This is the case if a
speed of 5 mph (8 km/h) is reached.
R High-speed level is not available.
These restrictions apply to all accessories
powered through a connection to the trailer power socket of your vehicle, e.g. a bicycle
carrier.
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. Leave enough play in the chains to make
tight cornering possible.
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. Towing a trailer
There are numerous legal requirements con-
cerning the towing of a trailer, e.g. speed
restrictions. Make sure that your car/trailer
combination complies with the local regula-
tions: R in your place of residence
R in the location to which you are driving
The police and local authorities can provide
reliable information.
Observe the following when towing a trailer:
R To gain driving experience and to become
accustomed to the new handling charac-
teristics, you should practice the following
in a traffic-free location:
- cornering
- stopping
- backing up
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 has electronically controlled
brakes, pull away carefully. Brake manually 260
Towing a trailerDriving and parking

using the brake controller and check
whether the brakes function correctly.
R Secure any objects on the trailer to prevent
the cargo from slipping when the vehicle is
in motion.
R When you couple up a trailer, check at reg-
ular intervals that the load is firmly secured.If the trailer is equipped with trailer lights
and brakes, check the trailer to ensure that
these are working.
R Bear in mind that the handling will be less
stable when towing a trailer than when driv- ing without one. Avoid sudden steering
movements.
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, do not brake suddenly, but
instead depress the brake pedal moder-
ately at first so that the trailer can activate its brakes. Then increase the pressure on
the brake pedal.
R If the automatic transmission repeatedly
shifts between gears on uphill or downhill
gradients, shift to a lower gear using the
left-hand steering wheel paddle shifter.
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 also be dissipated by
opening the windows and switching the ventilation blower and the interior temper-
ature to the highest level.
R When overtaking, pay particular attention
to the extended length of your vehicle/
trailer combination.
Due to the length of the vehicle/trailer
combination, you require additional road
space in relation to the vehicle you are
overtaking before you can change back to
the original lane. Decoupling a trailer
G
WARNING
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. G
WARNING
Vehicles with level control:
The vehicle is lowered as soon as you discon-
nect the trailer cable. This could result in your limbs or those of other people that are
between the vehicle body and tires or under-
neath the vehicle being trapped. There is a
risk of injury.
Make sure that nobody is in the immediate
vicinity of the wheel housings or under the
vehicle when you disconnect the trailer cable.
! 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 vehicle's electric parking brake.
X Start the engine.
X Close all doors and the tailgate.
X Apply the trailer's parking brake. Towing a trailer
261Driving and parking Z

X
Detach the trailer cable and decouple the
trailer.
X Switch off the engine. Permissible trailer loads and drawbar
loads
Weight specifications Maximum permissible gross vehicle
weight rating
The gross trailer weight is calculated by add-
ing the weight of the trailer to the weight of
the load and equipment on the trailer.
You will find installing dimensions and loads
under "Technical data" (Y page 459).
Permissible noseweight
You will find installing dimensions and loads
under "Technical data" (Y page 459).
Loading a trailer R
When loading the trailer, make sure that
neither the permissible gross weight of the
trailer nor the gross vehicle weight is
exceeded. The permissible gross vehicle
weight is indicated on the identification
plate on the B-pillar on the driver's side of
the vehicle.
You can find the maximum permissible val-
ues on the type plates of your vehicle and
the trailer. When calculating how much
weight the vehicle and trailer may carry,
pay attention to the respective lowest val-
ues.
R The trailer drawbar load on the ball coupling
must be added to the rear axle load to avoid exceeding the permissible gross axle
weight. The permissible gross vehicle
weight is indicated on the identification
plate on the B-pillar on the driver's side of
the vehicle.
i Mercedes-Benz recommends a trailer
load where the trailer drawbar noseweight accounts for 8% to 15% of the trailer's per-
missible gross weight.
i The weight of additional accessories, pas-
sengers, and cargo reduces the permissi-
ble trailer load and drawbar load for your
vehicle.
Checking the vehicle and trailer weight R
To check that the weights of the towing
vehicle and the trailer comply with the max-
imum permissible values, have the vehicle/
trailer combination (including the driver,
passengers, and cargo with a fully laden
trailer) weighed on a calibrated weigh-
bridge.
R Check the gross axle weight rating of the
front and rear axles, the gross weight of the
trailer and trailer drawbar load. Removing the ball coupling
X Remove the spring cotter.
X Remove the bolt from the ball coupling
recess.
X Remove the ball coupling from the ball cou-
pling recess.
X Clean the ball coupling if it is dirty.
X Stow the ball coupling so that it cannot be
thrown around.
Observe the loading guidelines (Y page 334)
and the safety notes regarding stowage
spaces (Y page 335).
Information on cleaning and care of the trailer tow hitch can be found at (Y page 376). Storing the ball coupling
G
WARNING
Do not carry the ball coupling in the vehicle
interior if it is not secured.
Otherwise, you and others could be injured by the ball coupling being thrown around if you: 262
Towing a trailerDriving an
d parking

Useful information
i This Operator's Manual describes all
models and all standard and optional equip- ment of your vehicle available at the time of
publication of the Operator's Manual.
Country-specific differences are possible.
Please note that your vehicle may not be
equipped with all features described. This
also applies to safety-related systems and
functions.
i Read the information on qualified special-
ist workshops (Y page 29). Important safety notes
G
WARNING
If you operate information systems and com-
munication equipment integrated in the vehi- cle while driving, you will be distracted from
traffic conditions. You could also lose control of the vehicle. There is a risk of an accident.
Only operate the equipment when the traffic
situation permits. If you are not sure that this
is possible, park the vehicle paying attention
to traffic conditions and operate the equip-
ment when the vehicle is stationary. G
WARNING
If the instrument cluster has failed or mal-
functioned, you may not recognize function
restrictions in systems relevant to safety. The operating safety of your vehicle may be
impaired. There is a risk of an accident.
Drive on carefully. Have the vehicle checked
at a qualified specialist workshop immedi-
ately.
You must observe the legal requirements for
the country in which you are currently driving when operating the on-board computer.
The on-board computer only shows messages
or warnings from certain systems in the mul- tifunction display. You should therefore make
sure your vehicle is operating safely at all times. Otherwise, a vehicle that is not oper-
ating safely may cause an accident.
For an overview, see the instrument panel
illustration (Y
page 35). Displays and operation
Instrument cluster lighting
The lighting in the instrument cluster, in the
displays and the controls in the vehicle inte-
rior can be adjusted using the brightness con-
trol knob.
The brightness control knob is located on the bottom left of the instrument cluster
(Y page 35).
X Turn the brightness control knob clockwise
or counter-clockwise.
If the light switch is set to 0058,0060or
0058, the brightness is dependent upon
the brightness of the ambient light.
i The light sensor in the instrument cluster
automatically controls the brightness of
the multifunction display.
In daylight, the displays in the instrument
cluster are not illuminated. Coolant temperature display
G
WARNING
Opening the hood when the engine is over-
heated or when there is a fire in the engine
compartment could expose you to hot gases
or other service products. There is a risk of
injury.
Let an overheated engine cool down before
opening the hood. If there is a fire in the
engine compartment, keep the hood closed
and contact the fire department.
! A display message is shown if the coolant
temperature is too high.
If the coolant temperature is over 248 ‡
(120 †), do not continue driving. The
engine will otherwise be damaged. 266
Displays and operationOn-board computer and displays

Display messages
Possible causes/consequences and
0050
0050Solutions 0049
Auto Auto
Lamp
LampFunction
Function
Inoperative
Inoperative The light sensor is defective.
X Visit a qualified specialist workshop. 0049
Switch Off Lights Switch Off Lights The lights are still switched on when you leave the vehicle. A
warning tone also sounds.
X Turn the light switch to 0058.Adaptive Highbeam Adaptive Highbeam
Assist Inoperative Assist Inoperative Adaptive Highbeam Assist is faulty.
X
Visit a qualified specialist workshop. Adaptive Highbeam Adaptive Highbeam
Assist Currently Assist Currently
Unavailable See Unavailable See
Operator's Manual Operator's Manual Adaptive Highbeam Assist is deactivated and temporarily inoper-
ative. Possible causes are:
R the windshield in the camera's field of vision is dirty.
R visibility is impaired due to heavy rain, snow or fog.
X Clean the windshield.
If the system detects that the camera is fully operational again, the
Adaptive Highbeam Assist Now Available
Adaptive Highbeam Assist Now Available message is dis-
played.
Adaptive Highbeam Assist is operational again. Engine
Display messages
Possible causes/consequences and
0050 0050Solutions 00BD
Check Coolant Check Coolant
Level See Opera‐ Level See Opera‐
tor's Manual tor's Manual The coolant level is too low.
! Avoid making long journeys with too little coolant in the engine
cooling system. The engine will otherwise be damaged.
X Add coolant, observing the warning notes before doing so
(Y page 369).
X If coolant needs to be added more often than usual, have the
engine coolant system checked at a qualified specialist work-
shop. 00AC The fan motor is faulty.
X At coolant temperatures below 248 ‡ (120 †), drive to the
nearest qualified specialist workshop.
X Avoid subjecting the engine to heavy loads, e.g. driving in moun-
tainous terrain, and stop-and-go traffic. 300
Display
messagesOn-board computer and displays