
BAS PLUS provides braking assistance in
hazardous situations with vehicles in front
within a speed range between 4 mph
(7 km/h) and 155 mph (250 km/h).
At speeds of up to approximately 44 mph
(70 km/h), BAS PLUS reacts to:
R stationary objects in the path of your
vehicle, e.g. stopped or parked vehicles
R pedestrians in the path of your vehicle
R objects crossing your path
i If BAS PLUS demands particularly high
braking force, preventative passenger
protection measures (PRE-SAFE ®
) are
activated simultaneously.
X Keep the brake pedal depressed until the
emergency braking situation is over.
ABS prevents the wheels from locking.
BAS PLUS is deactivated and the brakes
function as usual, if:
R you release the brake pedal
R there is no longer a risk of collision
R no obstacle is detected in front of your
vehicle
R you depress the accelerator pedal
R you activate kickdown COLLISION PREVENTION ASSIST
General notes COLLISION PREVENTION ASSIST consists of
the distance warning function and adaptive
Brake Assist, which are described in the
following section.
Distance warning function Important safety notes
i
Observe the "Important safety notes"
section (Y page 67). G
WARNING
The distance warning function does not react:
R to people or animals
R to oncoming vehicles
R to crossing traffic
R when cornering
Thus, the distance warning function cannot
provide a warning in all critical situations.
There is a risk of an accident.
Always pay careful attention to the traffic
situation and be ready to brake. G
WARNING
The distance warning function cannot always
clearly identify objects and complex traffic
situations.
In such cases, the distance warning function
may:
R give an unnecessary warning
R not give a warning
There is a risk of an accident.
Always pay careful attention to the traffic
situation and do not rely solely on the distance
warning function.
Function
X To activate/deactivate: activate or
deactivate the distance warning function in
the on-board computer (Y page 247).
If the distance warning function is not
activated, the æsymbol appears in the
assistance graphics display.
The distance warning function can help you
to minimize the risk of a front-end collision
with a vehicle ahead or reduce the effects of
such a collision. If the distance warning
function detects that there is a risk of a
collision, you will be warned visually and
acoustically. The distance warning function
cannot prevent a collision without your
intervention.
Starting at a speed of around 4 mph
(7 km/h), the distance warning function
warns you if you rapidly approach a vehicle in 70
Driving safety systemsSafety
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automatically increase the braking force to a
level suitable for the traffic conditions.
X Keep the brake pedal depressed until the
emergency braking situation is over.
ABS prevents the wheels from locking.
The brakes will work normally again if:
R you release the brake pedal
R there is no longer any danger of a rear-end
collision
R no obstacle is detected in front of your
vehicle
Adaptive Brake Assist is then deactivated.
Up to vehicle speeds of around 155 mph
(250 km/h), adaptive Brake Assist is capable
of reacting to moving objects that have
already been recognized as such at least once
over the period of observation. Adaptive
Brake Assist does not react to stationary
obstacles.
If Adaptive Brake Assist is not available due
to a malfunction in the radar sensor system,
the brake system remains available with full
brake boosting effect and BAS.
In particular, the detection of obstacles can
be impaired if there is:
R dirt on the sensors or anything else
covering the sensors
R snow or heavy rain
R interference by other radar sources
R there are strong radar reflections, for
example in parking garages
R a narrow vehicle traveling in front, e.g. a
motorbike
R a vehicle traveling in front on a different line
relative to the center of your vehicle
Following damage to the front end of the
vehicle, have the configuration and operation
of the radar sensor checked at a qualified
specialist workshop. This also applies to
collisions at low speeds where there is no
visible damage to the front of the vehicle. ESP
®
(Electronic Stability Program)
General notes i
Observe the "Important safety notes"
section (Y page 67).
ESP ®
monitors driving stability and traction,
i.e. power transmission between the tires and
the road surface.
If ESP ®
detects that the vehicle is deviating
from the direction desired by the driver, one
or more wheels are braked to stabilize the
vehicle. The engine output is also modified to
keep the vehicle on the desired course within
physical limits. ESP ®
assists the driver when
pulling away on wet or slippery roads. ESP ®
can also stabilize the vehicle during braking.
ETS/4ETS (Electronic Traction System) ETS/4ETS traction control is part of ESP
®
.
Traction control brakes the drive wheels
individually if they spin. This enables you to
pull away and accelerate on slippery surfaces,
for example if the road surface is slippery on
one side. In addition, more drive torque is
transferred to the wheel or wheels with
traction.
Traction control remains active, even if you
deactivate ESP ®
.
Important safety notes i
Observe the "Important safety notes"
section (Y page 67). G
WARNING
If ESP ®
is malfunctioning, ESP ®
is unable to
stabilize the vehicle. Additionally, further
driving safety systems are deactivated. This
increases the risk of skidding and an accident.
Drive on carefully. Have ESP ®
checked at a
qualified specialist workshop.
! Vehicles with 4MATIC: switch off the
ignition when the parking brake is being
tested on a brake dynamometer. 72
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X
Make sure that the surface of the battery is
free of lint, grease and other contaminants.
X Insert the front tabs of battery
compartment cover :into the housing
first and then press to close it.
X Insert mechanical key ;into the
SmartKey (Y page 84).
X Check the function of all SmartKey buttons
on the vehicle. 86
SmartKeyOpening and closing
ProCarManuals.com

!
When parking, pay particular attention to
objects above or below the sensors, such
as flower pots or trailer drawbars.
PARKTRONIC does not detect such objects
when they are in the immediate vicinity of
the vehicle. You could damage the vehicle
or the objects.
The sensors may not detect snow and other
objects that absorb ultrasonic waves.
Ultrasonic sources such as an automatic
car wash, the compressed-air brakes on a
truck or a pneumatic drill could cause
PARKTRONIC to malfunction.
PARKTRONIC may not function correctly on
uneven terrain.
PARKTRONIC is activated automatically when
you:
R switch on the ignition
R shift the transmission to position D,Ror N
R release the parking brake
PARKTRONIC is deactivated at speeds above
11 mph (18 km/h). It is reactivated at lower
speeds.
PARKTRONIC monitors the area around your
vehicle using six sensors in the front bumper
and six sensors in the rear bumper.
Range of the sensors General notes
PARKTRONIC does not take objects into
consideration that are:
R below the detection range, e.g. people,
animals or objects
R above the detection range, e.g.
overhanging loads, truck overhangs or
loading ramps. :
Sensors in the front bumper, left-hand
side (example)
The sensors must be free from dirt, ice or
slush. They can otherwise not function
correctly. Clean the sensors regularly, taking
care not to scratch or damage them
(Y page 346). Example: side view
Example: top view Driving systems
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ProCarManuals.com

You should always steer, brake or accelerate
yourself, in particular if warned by Lane
Keeping Assist.
If you fail to adapt your driving style, Lane
Keeping Assist can neither reduce the risk of
an accident nor override the laws of physics.
Lane Keeping Assist cannot take into account
the road, traffic and weather conditions. Lane
Keeping Assist is merely an aid. You are
responsible for the distance to the vehicle in
front, for vehicle speed, for braking in good
time and for staying in your lane.
The Lane Keeping Assist does not keep the
vehicle in the lane.
The system may be impaired or may not
function if:
R there is poor visibility, e.g. due to
insufficient illumination of the road, or due
to snow, rain, fog or spray
R there is glare, e.g. from oncoming traffic,
the sun or reflections (e.g. when the road
surface is wet)
R the windshield is dirty, fogged up, damaged
or covered, for instance by a sticker, in the
vicinity of the camera
R there are no, several or unclear lane
markings for a lane, e.g. in areas with road
construction work
R the lane markings are worn away, dark or
covered up, e.g. by dirt or snow
R the distance to the vehicle in front is too
small and the lane markings thus cannot be
detected
R the lane markings change quickly, e.g.
lanes branch off, cross one another or
merge
R the road is narrow and winding
R there are strong shadows cast on the lane
Switching on Lane Keeping Assist
X Switch on Active Lane Keeping Assist using
the on-board computer; to do so, select
Standard
Standard orAdaptive Adaptive (Ypage 248).
If you drive at speeds above 40 mph
(60 km/h) and lane markings are detected, the lines in the assistance graphics display
(Y
page 246) are shown in green. Lane
Keeping Assist is ready for use.
Standard
If Standard Standard is selected, no warning vibration
occurs if:
R you switch on the turn signals. In this event,
the warnings are suppressed for a certain
period of time.
R a driving safety system intervenes, such as
ABS, BAS or ESP ®
.
Adaptive
When Adaptive Adaptive is selected, no warning
vibration occurs if:
R you switch on the turn signals. In this event,
the warnings are suppressed for a certain
period of time.
R a driving safety system intervenes, e.g.
ABS, BAS or ESP ®
.
R you accelerate hard, e.g. kickdown.
R you brake hard.
R you steer actively, e.g. swerve to avoid an
obstacle or change lanes quickly.
R you cut the corner on a sharp bend.
In order that you are warned only when
necessary and in good time if you cross the
lane marking, the system recognizes certain
conditions and warns you accordingly.
The warning vibration occurs earlier if:
R you approach the outer lane marking on a
bend.
R the road has very wide lanes, e.g. a
highway.
R the system recognizes solid lane markings.
The warning vibration occurs later if:
R the road has narrow lanes.
R you cut the corner on a bend. Driving systems
229Driving and parking Z
ProCarManuals.com

situation. An inappropriate brake application
may be interrupted at any time if you:
R steer slightly in the opposite direction
R switch on the turn signal
R clearly brake or accelerate
A lane-correcting brake application is
interrupted automatically if:
R a driving safety system intervenes, e.g.
ESP ®
, PRE-SAFE ®
Brake or Active Blind
Spot Assist.
R lane markings can no longer be recognized.
Switching on Active Lane Keeping Assist
X Switch on Active Lane Keeping Assist using
the on-board computer; to do so, select
Standard
Standard orAdaptive Adaptive(Y page 248).
If you drive at speeds above 40 mph
(60 km/h) and lane markings are detected,
the lines in the assistance graphics display
(Y page 246) are shown in green. Active
Lane Keeping Assist is ready for use.
If Standard Standard is selected, no warning
vibration occurs if:
R you have switched on the turn signals. In
this event, the warnings are suppressed
for a certain period of time.
R a driving safety system intervenes, such
as ABS, BAS or ESP ®
.
When Adaptive
Adaptive is selected, no warning
vibration occurs if:
R you have switched on the turn signals. In
this event, the warnings are suppressed
for a certain period of time.
R a driving safety system intervenes, e.g.
ABS, BAS or ESP ®
.
R you accelerate hard, e.g. kickdown.
R you brake hard.
R you steer actively, e.g. swerve to avoid
an obstacle or change lanes quickly.
R you cut the corner on a sharp bend.
In order that you are warned only when
necessary and in good time if you cross the
lane marking, the system recognizes certain
conditions and warns you accordingly. The warning vibration occurs earlier if:
R
you approach the outer lane marking on a
bend.
R the road has very wide lanes, e.g. a
highway.
R the system recognizes solid lane markings.
The warning vibration occurs later if:
R the road has narrow lanes.
R you cut the corner on a bend. Driving systems
235Driving and parking Z
ProCarManuals.com

Safety systems
Display messages Possible causes/consequences and
M
MSolutions !÷
Currently Currently
Unavailable See Unavailable See
Operator's Manual Operator's Manual ABS (Anti-lock Braking System), ESP
®
(Electronic Stability
Program), BAS (Brake Assist), PRE-SAFE ®
, the HOLD function and
hill start assist are temporarily unavailable.
BAS PLUS, COLLISION PREVENTION ASSIST and
PRE-SAFE ®
Brake may also have failed.
In addition, the ÷,åand! warning lamps light up in
the instrument cluster.
ATTENTION ASSIST is deactivated.
For example, the on-board voltage may be insufficient.
G WARNING
The brake system continues to function normally, but without the
functions listed above. The wheels could therefore lock if you
brake hard, for example.
The steerability and braking characteristics may be severely
affected. The braking distance in an emergency braking situation
can increase.
If ESP ®
is not operational, ESP ®
is unable to stabilize the vehicle.
There is an increased risk of skidding and an accident.
X Drive on carefully.
If the display message disappears, the functions mentioned
above are available again.
If the display message continues to be displayed:
X Drive on carefully.
X Visit a qualified specialist workshop. !÷
Inoperative See Inoperative See
Operator's Manual Operator's Manual ABS, ESP
®
, BAS, PRE-SAFE ®
, the HOLD function and hill start
assist are unavailable due to a malfunction.
BAS PLUS, COLLISION PREVENTION ASSIST and
PRE-SAFE ®
Brake may also have failed.
The $ (USA only)/J (Canada only),÷,åand!
warning lamps in the instrument cluster also light up.
ATTENTION ASSIST is deactivated.
G WARNING
The brake system continues to function normally, but without the
functions listed above. The wheels could therefore lock if you
brake hard, for example.
The steerability and braking characteristics may be severely
affected. The braking distance in an emergency braking situation
can increase. 258
Display messagesOn-board computer and displays
ProCarManuals.com

Display messages Possible causes/consequences and
M
MSolutions T!
÷
Inoperative See Inoperative See
Operator's Manual Operator's Manual EBD (electronic brake force distribution), ABS, ESP
®
, BAS, PRE-
SAFE ®
, the HOLD function and hill start assist are unavailable due
to a malfunction.
BAS PLUS, COLLISION PREVENTION ASSIST and
PRE-SAFE ®
Brake may also have failed.
In addition, the ÷,åand! warning lamps light up in
the instrument cluster and a warning tone sounds.
G WARNING
The brake system continues to function normally, but without the
functions listed above. The front and rear wheels could therefore
lock if you brake hard, for example.
The steerability and braking characteristics may be severely
affected. The braking distance in an emergency braking situation
can increase.
If ESP ®
is not operational, ESP ®
is unable to stabilize the vehicle.
There is an increased risk of skidding and an accident.
X Drive on carefully.
X Visit a qualified specialist workshop immediately. F(USA
only)
J(Canada
only)
Please Release Please Release
Parking Brake Parking Brake You are driving with the parking brake applied. A warning tone also
sounds.
X
Release the parking brake. $(USA
only)
J(Canada
only)
Check Brake Fluid Check Brake Fluid
Level Level There is not enough brake fluid in the brake fluid reservoir.
In addition, the
$(USA only)/ J(Canada only) warning
lamp lights up in the instrument cluster and a warning tone
sounds.
G WARNING
The braking effect may be impaired.
There is a risk of an accident.
X Pull over and stop the vehicle safely as soon as possible, paying
attention to road and traffic conditions. Do not continue driving
under any circumstances.
X Secure the vehicle against rolling away ( Ypage 182).
X Consult a qualified specialist workshop.
X Do not add brake fluid. This does not correct the malfunction. 260
Display
messagesOn-board computer and displays
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