180Driving and operatingDrive systems
All-wheel drive
The All-wheel drive system enhances
driving characteristics and stability,
and helps to achieve the best
possible driveability regardless of
ground surface. The system is always
active and cannot be deactivated.
The torque is distributed steplessly
between the wheels of the front and
rear axle up to a torque split of 50%
to 50%. Depending on the driving
conditions, i.e. steady state driving,
All wheel drive system transfers a
minimum amount of torque for fuel
efficiency. Additionally the torque
vectoring between the rear wheels is
distributed depending on the vehicle
dynamic and surface.
This is possible because the All wheel drive system operates with two
clutches, one on each side.
For optimum system performance,
the vehicle's tyres should not have
varying degrees of wear.If a service message is displayed in
the Driver Information Centre, the
system may have limited functionality
(or be completely disabled in some
cases, i.e. the vehicle switches to
Front-wheel drive). Seek the
assistance of a workshop.
Towing the vehicle 3 279.Brakes
The brake system comprises two independent brake circuits.
If a brake circuit fails, the vehicle can
still be braked using the other brake
circuit. However, braking effect is
achieved only when the brake pedal
is depressed firmly. Considerably
more force is needed for this. The braking distance is extended. Seek
the assistance of a workshop before
continuing the journey.
When the engine is not running, the
support of the brake servo unit
disappears once the brake pedal has
been depressed once or twice.
Braking effect is not reduced, but
braking requires significantly greater
force. It is especially important to bear this in mind when being towed.
Control indicator R 3 109.
Active emergency braking 3 203.
Antilock brake system Antilock brake system (ABS)
prevents the wheels from locking.
Driving and operating181ABS starts to regulate brake pressure
as soon as a wheel shows a tendency to lock. The vehicle remains
steerable, even during hard braking.
ABS control is made apparent
through a pulse in the brake pedal
and the noise of the regulation
process.
For optimum braking, keep the brake
pedal fully depressed throughout the
braking process, despite the fact that
the pedal is pulsating. Do not reduce
the pressure on the pedal.
After starting off, the system performs a self-test which may be audible.
Control indicator u 3 110.
Adaptive brake light During full braking, all three brake
lights flash for the duration of ABS
control.
Fault9 Warning
If there is a fault in the ABS, the
wheels may be liable to lock due
to braking that is heavier than
normal. The advantages of ABS are no longer available. During
hard braking, the vehicle can no longer be steered and may
swerve.
Have the cause of the fault remedied
by a workshop.
Parking brake
9 Warning
Before leaving the vehicle, check
parking brake status. Control
indicator m must illuminate
constantly.
Electric parking brake
Applying when vehicle is stationary
9 Warning
Pull switch m for a minimum of
one second until control indicator
m illuminates constantly and
electric parking brake is applied
3 109. The electric parking brake
operates automatically with
adequate force.
Before leaving the vehicle, check
the electric parking brake status.
Control indicator m 3 109.
196Driving and operating9Warning
The Driver accepts full
responsibility to drive with the
appropriate following distance
based on traffic, weather, visibility and regional regulation. Followingdistance must be adjusted or the
system switched off when required by the prevailing conditions.
Adaptive cruise control in Sport
mode
On vehicles with Flex Ride driving
modes, the driver can slightly
increase the Adaptive cruise control
acceleration when Sport mode is
selected. This function can be
deactivated in the Flex Ride
visualisation menu 3 186
Detecting the vehicle ahead
The green illuminated vehicle ahead
control indicator A is displayed when
the system detects a vehicle in the driving path. The range of the sensors
is between 25 and 150 metres
depending on vehicle speed.
Forward collision alert 3 200.
If this symbol does not display, or
displays briefly, adaptive cruise
control will not respond to vehicles ahead.
Deactivation of the functionality
Adaptive cruise control is deactivated by the driver when:
● y is pressed.
● Brake pedal is applied.
● Clutch pedal is depressed for more than four seconds.
● Selector lever of automatic transmission is moved to N.
The system is also automatically
deactivated when:
● Vehicle speed accelerates above
190 km/h or slows down below
25 km/h . Vehicles with automatic
transmission slows down to a
stop without deactivating within
five minutes.
● The Traction Control system is deactivated or operating.
● The Electronic Stability Control is
deactivated or operating.
● There is no traffic and nothing detected on the road sides for
approx. one minute. In this case there are no radar echoes and
the sensor may report that it is blocked.
Driving and operating197● The active emergency brakingsystem is applying the brakes.
● Driving on steep inclines.
● The radar sensor is blocked by an ice or water film.
● A fault is detected in the radar, camera, engine or brake system.
● The brakes need to cool down.
Additionally, the system is
automatically deactivated on vehicles with automatic transmission (full
speed range adaptive cruise control)
when:
● The incline uphill or downhill is greater than 20 %.
● The electric parking brake is applied.
● The vehicle is being held to a stop
by the system for more than
five minutes.
● The vehicle stops, the driver's seat belt is unbuckled and thedriver's door is opened.When adaptive cruise control is
deactivated, the control indicator m
changes from green to white and a
pop-up message is displayed in the
Driver Information Centre.
The stored speed is maintained.
On Midlevel display, the stored speed is indicated in brackets in the Driver
Information Centre when the system
is deactivated but not switched off.
On Uplevel display, the adaptive
cruise control symbol C changes
from green to white when the system
is deactivated but not switched off.
9 Warning
When adaptive cruise control is
deactivated, the driver must take
over full brake and engine control
immediately.
Switching off the system
Press C to switch off adaptive cruise
control. The control indicator C
extinguishes in the Driver Information Centre. The stored speed is deleted.
Switching off the ignition also
switches off adaptive cruise control
and deletes the stored speed.
Driver's attention ● Use adaptive cruise control carefully on bends or mountain
roads, as it can lose the vehicle
ahead and needs time to detect it again.
● Do not use the system on slippery roads as it can create
rapid changes in tyre traction
(wheel spinning), so that you
could lose control of the vehicle.
● Do not use adaptive cruise control during rain, snow or
heavy dirt, as the radar sensor
can be covered by a water film,
dust, ice or snow. This reduces or suppresses completely the
198Driving and operatingvisibility. In case of sensor
blockage, clean the sensor
cover.
System limits9 Warning
The system's automatic brake
force does not permit hard braking and the braking level may not be
sufficient to avoid a collision.
● After a sudden lane change, the system needs a certain time to
detect the next preceding
vehicle. So if a new vehicle is
detected, the system may
accelerate instead of braking.
● Adaptive cruise control does ignore the oncoming traffic.
● Adaptive cruise control does not consider pedestrians and
animals for braking and driving
off.
● Adaptive cruise control considers
stopped vehicles only at low
speed.
● Do not use adaptive cruise control when towing a trailer.
● Do not use adaptive cruise control on roads with an incline ofmore than 10%.
Bends
The adaptive cruise control calculates
a predicted path based on the
centrifugal force. This predicted path
considers the current bend
characteristic, but cannot consider a
future bend change. The system may lose the current vehicle ahead or
consider a vehicle which is not in the
actual lane. This can happen when
entering or exiting a bend or if the
bend gets stronger or weaker. The
camera applies a certain correction
based on the detectable lane
markings. The control indicator A will
extinguish, if a vehicle ahead is no longer detected.
If the centrifugal force is too high in a
bend, the system slows down the
vehicle slightly. This braking level is
not designed to avoid spinning-off the
bend. The driver is responsible for
reducing the selected speed before
entering a bend and in general to
adapt the speed to the road type and
to existing speed limits.
Motorways
On motorways, adapt the set speed
to the situation and the weather.
Always consider that adaptive cruise
control has a limited visibility range, a
limited braking level and a certain
reaction time to verify if a vehicle is on
the driving path or not. Furthermore,
adaptive cruise control was designed to brake as late as possible to allow
changing the lane before the
automatic braking. Adaptive cruise
control may not be able to brake the
vehicle in time to avoid a collision with
200Driving and operatingaccident, consult a workshop to
verify and adjust the radar unit
position.
Settings
Settings can be changed in the
vehicle personalisation menu in the
Info-Display.
Select the relevant setting in Settings,
I Vehicle in the Info-Display.
Info-Display 3 121.
Vehicle personalisation 3 127.
Fault
If the adaptive cruise control does not
work due to temporary conditions
(e.g. blockage by ice, overheated
brakes or low speed manoeuvres) or
if there is a permanent system error,
a message is displayed in the Driver
Information Centre.
Vehicle messages 3 125.
Forward collision alert The forward collision alert may help toavoid or reduce the harm caused by
front-end crashes.
If the vehicle is equipped with
conventional cruise control, the
forward collision alert uses the front
camera in the windscreen to detect a
vehicle directly ahead, in your path.
If the vehicle is equipped with
adaptive cruise control, the forward
collision alert uses the radar sensor
and front camera to detect a vehicle
directly ahead, in your path.
A vehicle ahead is indicated by the
control indicator A.
If a vehicle directly ahead is
approached too quickly, a warning
chime and alert in the Driver
Information Centre is provided.
Additionally the driver gets notified by
a flashing red LED stripe or a pop up
symbol in the head-up display which
is projected on the windscreen in the
driver's field of view.
A precondition is that forward collision
alert in the vehicle personalisation
menu is not deactivated 3 127.
Activation
Forward collision alert with front
camera detects vehicles to distances
of approximately 60 metres and
operates automatically at all speeds
above walking speed.
Forward collision alert with radar
sensor detects vehicles to distances
of approximately 150 metres and
operates automatically at all speeds
above walking speed.
Alerting the driver The vehicle ahead control indicator
A illuminates green in the instrument
cluster when the system has detected
a vehicle in the driving path. On
vehicles with head-up display, A is
projected on the windscreen.
The control indicator A changes to
yellow when the distance to a
preceding moving vehicle gets too
small.
202Driving and operating
Note that the alert timing sensitivity
setting is shared with the following distance setting of the adaptive cruise control. So changing the alert timing
sensitivity changes the adaptive
cruise control following distance
setting.
Deactivation The system can be deactivated in the
personalisation menu, 3 127.
If the forward collision alert was
deactivated, alert sensitivity is set to
"medium" when ignition is switched on next time.
The last selected setting will be stored
when the ignition is switched off.
General information9 Warning
Forward collision alert is just a
warning system and does not
apply the brakes. When
approaching a vehicle ahead too
rapidly, it may not provide you
enough time to avoid a collision.
The driver accepts full
responsibility for the appropriate
following distance based on traffic, weather and visibility conditions.
The complete attention of the
driver is always required while
driving. The driver must always be
ready to take action and apply the
brakes.
System limitations
Forward collision alert is designed to warn on vehicles only, but may reactalso to other objects.
In the following cases, Forward
collision alert may not detect a vehicle ahead or sensor performance is
limited:
● Driving on winding or hilly roads.● During nighttime driving.
● Weather limits visibility, such as fog, rain, or snow
● The sensor in the windscreen is blocked by snow, ice, slush, mud,dirt, windscreen damage or
affected by foreign items, e.g.
stickers.
Following distance
indication
The following distance indication
displays the distance to a preceding
moving vehicle. The front camera in
the windscreen is used to detect the
distance of a vehicle directly ahead in
the vehicle's path. It is active at
speeds above 40 km/h.
When a preceding vehicle is detected ahead, the distance is indicated inseconds, displayed on a page in the
Driver Information Centre.
Driving and operating203On Baselevel display, choose Info
Menu ? via MENU on the turn
signal lever and turn the adjuster
wheel to choose following distance
indication page, 3 114
On Mid- and Uplevel display, select
Info menu via steering wheel buttons
and press å to select following
distance indication 3 114.
The minimum indicated distance is 0.5 seconds.
If there is no vehicle ahead or the vehicle ahead is out of range, two
dashes will be displayed: -.- sec.
If Adaptive cruise control is active,
this page shows the alert sensitivity
setting instead of following distance
setting. 3 192.
System limitations In the following cases, following
distance indication sensor
performance is limited:
● Driving on winding or hilly roads.
● During nighttime driving.
● Weather limits visibility, such as fog, rain, or snow.
● The sensor is blocked by snow, ice, slush, mud, dirt, windscreen
damage or affected by foreign
items, e.g. stickers.
Active emergency braking Active emergency braking can help toreduce the damage and injury from
crashes with vehicles, pedestrians and obstacles directly ahead, when a
collision can no longer be avoided
either by manual braking or by
steering. Before the active
emergency braking applies, the driver
is warned by the Forward collision
alert 3 200 or the Front pedestrian
protection alert 3 206.
The feature uses various inputs (e.g.
camera sensor, radar sensor, brake
pressure, vehicle speed) to calculate
the probability of a frontal collision.