MERCEDES-BENZ M-Class 2015 W166 Repair Manual

If the restraint system control unit detects a
high accident severity, additional compo-
nents of the restraint system are activated
independently of one another in certain fron- tal collision situations:
R Front air bags and driver's knee bag
R Windowbag, if the system determines that
it can offer additional protection to that
provided by the seat belt
Depending on the person occupying the front-
passenger seat, the front-passenger air bag is activated or deactivated. The front-passenger front air bag can only be deployed in an acci-
dent if the PASSENGER AIR BAG OFF indica-
tor lamp is off. Observe the information on the
PASSENGER AIR BAG OFF indicator lamp
(Y page 45).
Your vehicle has two-stage front air bags.
During the first deployment stage, the front
air bag fills with propellant gas which reduces
the risk of injury. The second stage is then
triggered within milliseconds, filling the front
air bag with the maximum amount of propel-
lant gas.
The deployment thresholds for the Emer-
gency Tensioning Devices and air bags are
calculated on the basis of the vehicle decel-
eration or acceleration occurring at various
points in the vehicle. This process is pre-emp- tive in nature. The air bag must be deployed
on time, at the start of the collision.
The rate of vehicle deceleration or accelera-
tion and the direction of the force are essen-
tially determined by:
R distribution of the force during the impact
R collision angle
R deformation characteristics of the vehicle
R characteristics of the object with which the
vehicle has collided
Factors which can only be seen and measured
after the collision has occurred do not play a
decisive role in the deployment of an airbag,
nor do they provide an indication of air bag
deployment. The vehicle may be considerably deformed
without an air bag being deployed. This is the
case if only relatively easily deformable parts
have been hit and a high rate of deceleration
has not been reached. Conversely, an air bag may be deployed even though the vehicle suf-
fers only minor deformation. This is the case
if, for example, very rigid vehicle parts such as
the longitudinal body members are hit in an
accident and the rate of deceleration is suffi-
cient.
If the restraint system control unit detects a
side impact or an overturn situation, the rel-
evant restraint system components are acti-
vated independently of one another depend-
ing on the apparent type of accident. If addi-
tional protection for the vehicle occupants is determined in this situation, the belt tension-
ers are also triggered.
R Side impact air bags on the side of the col-
lision, regardless of Emergency Tensioning
Device and use of the seat belt on the driv-
er's side and the outer seats on the second row
The sidebag on the front-passenger side
deploys under the following conditions:
- the OCS system detects that the front-
passenger seat is occupied or
- the belt tongue has engaged in the belt
buckle of the front-passenger seat.
R Window curtain air bag on the side of the
collision, regardless of seat belt use and
whether front-passenger seat is occupied
R Windowbags on the driver's and front-
passenger sides in certain overturn situa-
tions if the system determines that they
can offer additional protection to that pro-
vided by the seat belt
i Not all air bags are deployed in an acci-
dent. The various air bag systems work
independently of each other. Occupant safety
59Safety Z

How the air bag system works is deter-
mined by the severity of the accident detec- ted, especially the vehicle deceleration or
acceleration, and the apparent type of acci- dent:
R frontal collision
R side impact
R rollover PRE-SAFE
®
(anticipatory occupant
protection system)
Introduction In certain hazardous situations, PRE-SAFE
®
takes pre-emptive measures to protect the
vehicle occupants.
Important safety notes !
Make sure that there are no objects in the
footwell or behind the seats. There is a dan- ger that the seats and/or objects could be
damaged when PRE-SAFE ®
is activated.
Although your vehicle is equipped with PRE-
SAFE ®
, the possibility of injury in the event of
an accident cannot be ruled out. Always
adapt your driving style to suit the prevailing
road and weather conditions and maintain a
safe distance from the vehicle in front. Drive
carefully.
Function PRE-SAFE
®
intervenes:
R in emergency braking situations, e.g. when
BAS is activated
R in critical driving situations, e.g. when phys-
ical limits are exceeded and the vehicle
understeers or oversteers severely
R on vehicles with the Active Driving Assis-
tance package: if BAS PLUS intervenes
powerfully or the radar sensor system
detects an imminent danger of collision in
certain situations PRE-SAFE
®
takes the following measures
depending on the hazardous situation detec-
ted:
R the front seat belts are pre-tensioned.
R if the vehicle skids, the sliding sunroof and
the side windows are closed so that only a
small gap remains. The panorama roof with power tilt/sliding panel is completely
closed.
R vehicles with the memory function: the
front-passenger seat is adjusted if it is in an
unfavorable position.
R vehicles with a multicontour seat: the air
pressure in the side bolsters of the seat
backrest is increased.
If the hazardous situation passes without
resulting in an accident, PRE-SAFE ®
slackens
the belt pre-tensioning. On vehicles with mul-
ticontour seats, the air pressure in the side
bolsters is reduced again. All settings made
by PRE-SAFE ®
can then be reversed.
If the seat belt pre-tensioning is not reduced:
X Move the seat backrest or seat back
slightly when the vehicle is stationary.
The seat belt pre-tensioning is reduced and
the locking mechanism is released.
The seat-belt adjustment is an integral part of
the PRE-SAFE ®
convenience function. Infor-
mation about the convenience function can
be found under "Belt adjustment"
(Y page 49). Automatic measures after an acci-
dent
Immediately after an accident, the following
measures are implemented, depending on
the type and severity of the impact:
R by activating the hazard warning lamps
R the emergency lighting is activated
R the vehicle doors are unlocked
R the front side windows are lowered 60
Occupant safetySafety

R
in vehicles with a memory function: the
electrically adjustable steering wheel is
raised
R the engine is switched off
R vehicles with mbrace: automatic emer-
gency call Children in the vehicle
Important safety notes
Accident statistics show that children
secured in the rear seats are safer than chil-
dren secured in the front-passenger seat. For this reason, Mercedes-Benz strongly advises
that you install a child restraint system on a
rear seat. Children are generally better pro-
tected there.
If a child younger than 12 years and under 5 ft
(1.50 m) in height is traveling in the vehicle:
R always secure the child in a child restraint
system suitable for Mercedes-Benz vehi-
cles. The child restraint system must be
appropriate to the age, weight and size of
the child
R be sure to observe the instructions and
safety notes in this section in addition to
the child restraint system manufacturer's
installation instructions
R be sure to observe the instructions and
safety notes on the "Occupant classifica-
tion system (OCS)" (Y page 53)G
WARNING
If you leave children unsupervised in the vehi- cle, they could set it in motion by, for example:
R release the parking brake.
R shift the automatic transmission out of the
parking position P.
R start the engine.
In addition, they may operate vehicle equip-
ment and become trapped. There is a risk of
an accident and injury. When leaving the vehicle, always take the
SmartKey with you and lock the vehicle. Never
leave children unsupervised in the vehicle. G
WARNING
If persons, particularly children are subjected to prolonged exposure to extreme heat or
cold, there is a risk of injury, possibly even
fatal. Never leave children unattended in the
vehicle. G
WARNING
If the child restraint system is subjected to
direct sunlight, parts may get very hot. Chil-
dren may burn themselves on these parts,
particularly on the metal parts of the child
restraint system. There is a risk of injury.
If you leave the vehicle, taking the child with
you, always ensure that the child restraint
system is not exposed to direct sunlight. Pro- tect it with a blanket, for example. If the child
restraint system has been exposed to direct
sunlight, let it cool down before securing the
child in it. Never leave children unattended in the vehicle.
Always ensure that all vehicle occupants have
their seat belts fastened correctly and are sit- ting properly. Particular attention must be
paid to children.
Observe the safety notes on the seat belt
(Y page 46) and the notes on correct use of
seat belts (Y page 47).
A booster seat may be necessary to achieve
proper seat belt positioning for children over
41 lbs (18 kg) or until they reach a height
where a lap/shoulder belt fits properly with-
out a booster seat. Special seat belt retractor
G
WARNING
If the seat belt is released while driving, the
child restraint system will no longer be
secured properly. The special seat belt retrac- tor is disabled and the inertia real draws in a Children in the vehicle
61Safety
Z

portion of the seat belt. The seat belt cannot
be immediately refastened. There is an
increased risk of injury, possibly even fatal.
Stop the vehicle immediately, paying atten-
tion to road and traffic conditions. Reactivate the special seat belt retractor and secure the
child restraint system properly.
All seat belts in the vehicle, except the driv-
er's seat belt, are equipped with a special seat belt retractor. When activated, the special
seat belt retractor ensures that the seat belt
cannot slacken once the child seat is secured.
Installing a child restraint system:
X Make sure you observe the child restraint
system manufacturer's installation instruc-
tions.
X Pull the seat belt smoothly from the belt
outlet.
X Engage seat belt tongue in belt buckle.
Activating the special seat belt retractor:
X Pull the seat belt out fully and let the inertia
reel retract it again.
While the seat belt is retracting, you should hear a ratcheting sound. The special seat
belt retractor is enabled.
X Push the child restraint system down so
that the seat belt is tight and does not
loosen.
Removing a child restraint system/deactivat-
ing the special seat belt retractor:
X Make sure you observe the child restraint
system manufacturer's installation instruc- tions.
X Press the belt buckle release button, hold
the belt tongue and guide it back towards
the belt outlet.
The special seat belt retractor is deactiva-
ted. Child restraint system
The use of seat belts and child restraint sys-
tems is required by law in:
R all 50 states
R the U.S. territories
R the District of Columbia
R all Canadian provinces
If you install a rearward-facing child restraint
system on the center rear seat, the rear arm
rest must be folded back as far as possible.
You can obtain further information about the correct child restraint system from any
authorized Mercedes-Benz Center. G
WARNING
If the child restraint system is installed incor- rectly on a suitable seat, it cannot protect as
intended. The child cannot then be restrained in the event of an accident, heavy braking or
sudden changes of direction. There is an
increased risk of injury, possibly even fatal.
Make sure that you observe the child restraint
system manufacturer's installation instruc-
tions and the notes on use. Please ensure,
that the base of the child restraint system is
always resting completely on the seat cush-
ion. Never place objects, e.g. cushions, under or behind the child restraint system. Only use
child restraint systems with the original cover
designed for them. Only replace damaged
covers with genuine covers. G
WARNING
If the child restraint system is installed incor- rectly or is not secured, it can come loose in
the event of an accident, heavy braking or a
sudden change in direction. The child
restraint system could be thrown about, strik- ing vehicle occupants. There is an increased
risk of injury, possibly even fatal.
Always install child restraint systems prop-
erly, even if they are not being used. Make
sure that you observe the child restraint sys-
tem manufacturer's installation instructions. 62
Children in the vehicleSafety

You will find further information on stowing
objects, luggage or loads under "Loading
guidelines" (Y page 334). G
WARNING
Child restraint systems or their securing sys-
tems which have been damaged or subjected to a load in an accident can no longer protect
as intended. The child cannot then be
restrained in the event of an accident, heavy
braking or sudden changes of direction. There is an increased risk of injury, possibly even
fatal.
Replace child restraint systems which have
been damaged or subjected to a load in an
accident as soon as possible. Have the secur-
ing systems on the child restraint system
checked at a qualified specialist workshop,
before you install a child restraint system
again.
If it is absolutely necessary to carry a child on the front-passenger seat, be sure to observe
the information on the "Occupant Classifica-
tion System (OCS)" (Y page 53). There you
will also find information on deactivating the
front-passenger front air bag.
All child restraint systems must meet the fol- lowing standards:
R U.S. Federal Motor Vehicle Safety Stand-
ards 213 and 225
R Canadian Motor Vehicle Safety Standards
213 and 210.2
Confirmation that the child restraint system
corresponds to the standards can be found
on an instruction label on the child restraint
system. This confirmation can also be found
in the installation instructions that are inclu-
ded with the child restraint system.
Observe the warning labels in the vehicle inte-
rior and on the child restraint system. LATCH-type (ISOFIX) child seat secur-
ing system G
WARNING
LATCH-type (ISOFIX) child restraint systems
do not offer sufficient protective effect for
children whose weight is greater than 48 lbs
(22 kg) who are secured using the safety belt integrated in the child restraint system. In the
event of an accident, a child might not be
restrained correctly. This poses an increased
risk of injury or even fatal injury.
If the child weighs more than 48 lbs (22 kg),
only use LATCH-type (ISOFIX) child restraint
systems with which the child is also secured
with the vehicle seat belt. Also secure the
child restraint system with the Top Tether
belt, if available.
Always comply with the manufacturer's
installation and operating instructions for the child restraint system used.
Before every trip, make sure that the LATCH- type (ISOFIX) child restraint system is
engaged correctly in both LATCH-type (ISO-
FIX) securing rings
! When installing the child restraint system,
make sure that the seat belt for the middle seat does not get trapped. The seat belt
could otherwise be damaged. 0043
LATCH-type (ISOFIX) securing rings
X Install the LATCH-type (ISOFIX) child
restraint system on both LATCH-type (ISO-
FIX) securing rings 0043. Children in the vehicle
63Safety Z

ISOFIX is a standardized securing system for
specially designed child restraint systems on
the rear seats. LATCH-type (ISOFIX) securing rings 0043for two LATCH-type (ISOFIX) child
restraint systems are installed on the left and
right rear seats.
Non-LATCH-type (ISOFIX) child seats may
also be used and can be installed using the
vehicle's seat belt system. Install child seats
according to the manufacturer's instructions. Top Tether
Introduction Top Tether provides an additional connection
between a child restraint system, secured
with a LATCH-type (ISOFIX) child seat mount,and the rear seat. This helps reduce the risk of
injury even further. If the child restraint sys-
tem has a Top Tether belt, this should be used at all times.
Important safety notes G
WARNING
If the rear seats or the rear seat backrests are not locked, they could fold forwards in the
event of an accident, heavy braking or sudden changes of direction. As a result, child
restraint systems cannot perform their inten-
ded protective function. Rear seats and rear
seat backrests that are not locked can also
cause additional injuries, e.g. in the event of
an accident. This poses an increased risk of
injury or even fatal injury.
Always lock the rear seats and rear seat
backrests after installing a Top Tether belt.
Observe the lock verification indicator. Adjust the rear seat backrests so that they are in an
upright position. Top Tether anchorage points
Top Tether anchorage points
0085are on the
rear side of the rear seat backrests. X
Move head restraint 0087upwards.
X Fit the LATCH-type (ISOFIX) child restraint
system with Top Tether. Make sure you
observe the child restraint system manu-
facturer's installation instructions.
X Route Top Tether belt 0084under head
restraint 0087between both head restraint
bars.
X Guide Top Tether belt 0084downward
between cargo compartment cover 0043and
rear seat backrests 0044.
X Hook Top Tether hook 0083of Top Tether belt
0084 into Top Tether anchorage 0085.
Make sure that:
R Top Tether hook 0083is hooked into Top
Tether anchorage 0085, as shown
R Top Tether belt 0084is not twisted
R when cargo compartment cover 0043is
installed, Top Tether belt 0084, runs64
Children in the vehicleSafety

between rear seat backrests
0044and
cargo compartment cover 0043
R when the safety net is installed, Top
Tether belt 0084runs between rear seat
backrests 0044and the safety net.
X Tension Top Tether belt 0084. Make sure you
observe the child restraint system manu-
facturer's installation instructions.
X If necessary, push head restraint 0087back
down slightly (Y page 108). Make sure you
do not interfere with the correct routing of
Top Tether belt 0084. Child restraint system on the front-
passenger seat
General notes Accident statistics show that children
secured in the rear seats are safer than chil-
dren secured in the front-passenger seat. For this reason, Mercedes-Benz strongly advises
that you install a child restraint system on a
rear seat.
If it is absolutely necessary to install a child
restraint system to the front-passenger seat,
be sure to observe the instructions and safety
notes on the "Occupant classification system (OCS)" (Y page 53).
You can thus avoid the risks that could arise
as a result of:
R an incorrectly categorized person in the
front-passenger seat
R the unintentional deactivation of the front-
passenger front air bag
R the unsuitable positioning of the child
restraint system, e.g. too close to the dash-
board
Rearward-facing child restraint system If it is absolutely necessary to install a rear-
ward-facing child restraint system on the
front-passenger seat, always make sure that
the front-passenger front air bag is deactiva-
ted. Only if the PASSENGER AIR BAG OFF indicator lamp is permanently lit (Y
page 45)
is the front-passenger front air bag deactiva-
ted.
Always observe the child restraint system
manufacturer's installation and operating
instructions.
Forward-facing child restraint system If it is absolutely necessary to install a
forward-facing child restraint system on the
front-passenger seat, always move the front-
passenger seat as far back as possible. The
entire base of the child restraint system must always rest on the seat cushion of the front-
passenger seat. The backrest of the child
restraint system must, as far as possible, lie
flat against the backrest of the front-
passenger seat. The child restraint system
must not touch the roof or be put under strain
by the head restraint. Adjust the angle of the
seat backrest and the head restraint position accordingly. Always make sure that the shoul-
der belt strap is correctly routed from the
vehicle belt sash guide to the shoulder belt
guide on the child restraint system. The shoul- der belt strap must be routed forwards and
downwards from the vehicle belt sash guide.
If necessary, adjust the vehicle belt sash
guide and the front-passenger seat accord-
ingly.
Always observe the child restraint system
manufacturer's installation and operating
instructions. Children in the vehicle
65Safety Z

Child-proof locks
Important safety notes G
WARNING
If children are traveling in the vehicle, they
could:
R open doors, thus endangering other people
or road users
R exit the vehicle and be caught by oncoming
traffic
R operate vehicle equipment and become
trapped
There is a risk of an accident and injury.
Always activate the child-proof locks and
override feature if children are traveling in the vehicle. When leaving the vehicle, always take
the key with you and lock the vehicle. Never
leave children unattended in the vehicle.
Override feature for: R the rear doors (Y page 66)
R the rear side windows (Y page 67)G
WARNING
If you leave children unsupervised in the vehi- cle, they could set it in motion by, for example:
R release the parking brake.
R shift the automatic transmission out of the
parking position P.
R start the engine.
In addition, they may operate vehicle equip-
ment and become trapped. There is a risk of
an accident and injury.
When leaving the vehicle, always take the
SmartKey with you and lock the vehicle. Never
leave children unsupervised in the vehicle. G
WARNING
If persons, particularly children are subjected to prolonged exposure to extreme heat or
cold, there is a risk of injury, possibly even
fatal. Never leave children unattended in the
vehicle. G
WARNING
If the child restraint system is subjected to
direct sunlight, parts may get very hot. Chil-
dren may burn themselves on these parts,
particularly on the metal parts of the child
restraint system. There is a risk of injury.
If you leave the vehicle, taking the child with
you, always ensure that the child restraint
system is not exposed to direct sunlight. Pro- tect it with a blanket, for example. If the childrestraint system has been exposed to direct
sunlight, let it cool down before securing the
child in it. Never leave children unattended in the vehicle.
Child-proof locks for the rear doors You secure each door individually with the
child-proof locks on the rear doors. A door
secured with a child-proof lock cannot be
opened from inside the vehicle. When the
vehicle is unlocked, the door can be opened
from the outside.
X To activate: press the child-proof lock
lever up in the direction of arrow 0043.
X Make sure that the child-proof locks are
working properly.
X To deactivate: press the child-proof lock
lever down in the direction of arrow 0044.66
Children in the vehicleSafety

Override feature for the rear side win-
dows X
To activate/deactivate: press button0043.
If indicator lamp 0044is lit, operation of the
rear side windows is disabled. Operation is
only possible using the switches in the driv- er's door. If indicator lamp 0044is off, oper-
ation is possible using the switches in the
rear compartment. Pets in the vehicle
G
WARNING
If you leave animals unattended or unsecured in the vehicle, they could press buttons or
switches, for example.
As a result, they could:
R activate vehicle equipment and become
trapped, for example
R activate or deactivate systems, thereby
endangering other road users
Unsecured animals could also be flung around
the vehicle in the event of an accident or sud- den steering or braking, thereby injuring vehi-
cle occupants. There is a risk of an accident
and injury.
Never leave animals unattended in the vehi-
cle. Always secure animals properly during
the journey, e.g. use a suitable animal trans-
port box. Driving safety systems
Overview of driving safety systems
In this section, you will find information about the following driving safety systems:
R ABS ( Anti-lock BrakingSystem)
(Y page 68)
R BAS ( Brake Assist System) (Y page 68)
R BAS PLUS ( BrakeAssist System Plus)
(Y page 69)
R COLLISION PREVENTION ASSIST (distance
warning function and adaptive Brake
Assist) (Y page 70)
R ESP ®
(Electronic StabilityProgram)
(Y page 73)
R EBD ( Electronic Brake force Distribution)
(Y page 75)
R ADAPTIVE BRAKE (Y page 75)
R PRE-SAFE ®
Brake (Y page 75)
R STEER CONTROL (Y page 77) Important safety notes
If you fail to adapt your driving style or
become distracted, the driving safety sys-
tems can neither reduce the risk of accident
nor override the laws of physics. Driving
safety systems are merely aids designed to
assist driving. You are responsible for the dis-
tance to the vehicle in front, for vehicle speed and for braking in good time. Always adapt
your driving style to suit the prevailing road
and weather conditions and maintain a safe
distance from the vehicle in front. Drive care-
fully.
i The driving safety systems described only
work as effectively as possible when there
is adequate contact between the tires and
the road surface. Please pay special atten- tion to the notes on tires, recommended
minimum tire tread depths, etc.
(Y page 400).
In wintry driving conditions, always use
winter tires (M+S tires) and if necessary, Driving safety systems
67Safety Z

snow chains. Only in this way will the driv-
ing safety systems described in this section
work as effectively as possible. ABS (Anti-lock Braking System)
General information ABS regulates brake pressure in such a way
that the wheels do not lock when you brake.
This allows you to continue steering the vehi-
cle when braking.
The 0025 ABS warning lamp in the instrument
cluster lights up when the ignition is switched on. It goes out when the engine is running.
Important safety notes i
Observe the "Important safety notes" sec-
tion (Y page 67). G
WARNING
If ABS is faulty, the wheels could lock when
braking. The steerability and braking charac-
teristics may be severely impaired. Addition-
ally, further driving safety systems are deac-
tivated. There is an increased danger of skid- ding and accidents.
Drive on carefully. Have ABS checked imme-
diately at a qualified specialist workshop.
When ABS is malfunctioning, other systems,
including driving safety systems, will also
become inoperative. Observe the information on the ABS warning lamp (Y page 320) and
display messages which may be shown in the
instrument cluster (Y page 285).
ABS works from a speed of about 5 mph
(8 km/h), regardless of road-surface condi-
tions. ABS works on slippery surfaces, even
when you only brake gently. Braking X
If ABS intervenes: continue to depress the
brake pedal vigorously until the braking sit- uation is over.
X To make a full brake application:
depress the brake pedal with full force.
If ABS intervenes when braking, you will feel a
pulsing in the brake pedal.
The pulsating brake pedal can be an indica-
tion of hazardous road conditions, and func-
tions as a reminder to take extra care while
driving.
Off-road ABS An ABS system specifically suited to off-road
terrain is activated automatically once the off-
road program is activated (Y page 251).
At speeds below 20 mph (30 km/h), the front
wheels lock cyclically during braking. The dig-
ging-in effect achieved in the process reduces the stopping distance on off-road terrain. This
limits steering capability. BAS (Brake Assist System)
General information BAS operates in emergency braking situa-
tions. If you depress the brake pedal quickly,
BAS automatically boosts the braking force,
thus shortening the stopping distance.
Important safety notes i
Observe the "Important safety notes" sec-
tion (Y page 67). G
WARNING
If BAS is malfunctioning, the braking distance
in an emergency braking situation is
increased. There is a risk of an accident.
In an emergency braking situation, depress
the brake pedal with full force. ABS prevents
the wheels from locking. 68
Driving safety systemsSafety