2020 MERCEDES-BENZ METRIS brake sensor

Useful information
This Operator's Manual describes all models
as well as standard and optional equipment of
your vehicle that were available at the time of
going to print. Country-specific variations are
possible. Note that your vehicle may not be
equipped with all of the described functions.
This also applies to systems and functions rel-
evant to safety.
Read the information on qualified specialist
workshops (Y page
32).Breaking-in notes
Important safety notes
In certain driving and driving safety systems,
the sensors adjust automatically while a cer-
tain distance is being driven after the vehicle
has been delivered or after repairs. Full system
effectiveness is not reached until the end of
this teach-in procedure.
New or replaced brake pads and brake discs
only reach their optimal braking effect after a
few hundred kilometers of driving. Until then,
compensate for this by applying greater force
to the brake pedal. The first 1000 miles (1500 km)
For the service life and economy of your vehi-
cle it is crucial that you break in the engine
with due care.
R Therefore, protect the engine for the first
1000 miles (1500 km

) by driving at varying
vehicle and engine speeds.
R Avoid overstraining the vehicle and high
engine speeds during this period, e.g. driv-
ing at full throttle. Do not exceed Ø of the
permissible maximum speed for each gear.
R Do not change down a gear manually in
order to brake.
R Try to avoid depressing the accelerator
pedal beyond the pressure point (kickdown).
After 1000 miles (1500 km), you can increase
the engine speed gradually and accelerate the
vehicle to full speed.
i You should also observe these notes on
breaking-in if the engine or parts of the drive
train on your vehicle have been replaced. Driving
Important safety notes
G
WARNING
Flammable materials introduced through
environmental influence or by animals can
ignite if in contact with the exhaust system
or parts of the engine that heat up. There is
a risk of fire.
Carry out regular checks to make sure that
there are no flammable foreign materials in
the engine compartment or in the exhaust
system. G
WARNING
If you switch off the ignition while driving,
safety-relevant functions are only available
with limitations, or not at all. This could
affect, for example, the power steering and
the brake boosting effect. You will require
considerably more effort to steer and brake.
There is a risk of an accident.
Do not switch off the ignition while driving. G
WARNING
If the parking brake has not been fully
released when driving, the parking brake
can:
R overheat and cause a fire
R lose its hold function.
There is a risk of fire and an accident.
Release the parking brake fully before driv-
ing off.
! Warm up the engine quickly. Do not use
the engine's full performance until it has
reached operating temperature.
Only shift the automatic transmission to the
desired drive position when the vehicle is
stationary.
Where possible, avoid spinning the drive
wheels when pulling away on slippery roads.
You could otherwise damage the drive train. 126
Driving
Driving and parking

of the journey. Make sure that you do not
endanger other road users when doing so.
Checking the brake pad thickness In addition to monitoring using the brake pad
wear sensor, regularly monitor and check all of
the brake pads by performing a visual inspec-
tion to look for pad material wear.
If you are unable to check the brake wear on
the inside of the wheels, remove the wheels
with the tools provided.
Make sure that the brake pad material thick-
ness never falls below
0.12 in (3 mm). Have
the brake pads checked and replaced at a
qualified specialist workshop, if necessary.
Do not solely rely on the brake pad wear sen-
sor.
It is strongly recommended that you have the
brake pads checked at a qualified specialist
workshop at every service displayed in the
maintenance interval indicator, prior to long
journeys and whenever the wheels are
removed.
New brake discs and brake pads/
linings New brake pads and brake discs only reach
their optimal braking effect after about
60 miles

(100 kilometers). Until then, compen-
sate for this by applying greater force to the
brake pedal.
For safety reasons, Mercedes-Benz recom-
mends only installing the following brake discs
and brake pads/linings:
R brake discs that have been approved by
Mercedes-Benz
R brake pads/linings that have been approved
by Mercedes-Benz or are of an equivalent
standard of quality
Other brake discs or brake pads/linings can
compromise the safety of your vehicle.
Always replace all brake discs or brake pads/
linings on an axle at the same time and only
have them replaced at a qualified specialist
workshop. When replacing the brake discs,
always have the brake pads/linings replaced
at the same time. Parking brake G
WARNING
If you must brake the vehicle with the park-
ing brake, the braking distance is considera-
bly longer and the wheels could lock. There
is an increased danger of skidding and acci-
dents.
Only use the parking brake to brake the
vehicle when the service brake is faulty. Do
not apply the parking brake too firmly. If the
wheels lock, release the parking brake until
the wheels begin turning again.
When driving on wet roads or dirt-covered sur-
faces, road salt and/or dirt may get into the
parking brake. This causes corrosion and a
reduction of braking force.
In order to prevent this, drive with the parking
brake lightly applied from time to time. When
doing so, drive for a distance of approximately
110 yds (100 m) at a maximum speed of
12 mph (20 km/h

).
The brake lamps are not illuminated when you
brake the vehicle using the parking brake. Driving in wet conditions
Hydroplaning G
WARNING
There is a danger of hydroplaning occurring,
even if you are driving slowly and your tires
have sufficient tread depth, depending on
the depth of water on the road. There is a
risk of an accident.
For this reason, avoid tire ruts and brake
carefully.
Therefore, in heavy rain or other conditions in
which hydroplaning can occur, drive as fol-
lows:
R reduce your speed
R avoid tire ruts
R apply the brakes with care Driving tips
143
Driving and parking Z

R
you shift to neutral i while the vehicle is in
motion
R ESP ®
intervenes or you deactivate ESP ®
R there is a malfunction in the ESP ®
or ABS
system
If cruise control automatically deactivates, a
warning tone sounds and the Cruise Con‐
trol Off message appears briefly in the dis-
play.
The V symbol and the display of the stored
speed in the header or in the status area of
the display are then not shown.
Problems with cruise control The speed cannot be set when cruise control
is activated.
The display is showing a message of high pri-
ority and cannot therefore show a change in
speed.
X Proceed as instructed by the message in the
display. COLLISION PREVENTION ASSIST
General notes COLLISION PREVENTION ASSIST helps you:
R to minimize the risk of a front-end collision
with a detected obstacle in the path of your
vehicle
R to reduce the consequences of a collision
with the vehicle in front
The system uses radar sensors to detect vehi-
cles in front.
COLLISION PREVENTION ASSIST consists of
the distance warning function and Adaptive
Brake Assist.
If COLLISION PREVENTION ASSIST is malfunc-
tioning, the display shows a corresponding
message
(Y page 222). Distance warning function Important safety notes
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
The distance warning function may not give
warnings in all critical situations. There is a
risk of an accident.
Always pay careful attention to the traffic
situation and be ready to brake.
Always adapt your speed to suit the prevail-
ing road and traffic conditions. 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 dis-
tance warning function.
In particular, the detection of obstacles can be
impaired in the case of: R dirt on the sensors or anything else covering
the sensors
R snow or heavy rain
R interference from other radar sources
R 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
Due to the nature of the system, particularly
complicated but non-critical driving conditions Driving systems
149
Driving and parking Z

may also cause the system to display a warn-
ing.
If you fail to adapt your driving style, the dis-
tance warning function can neither reduce the
risk of an accident nor override the laws of
physics. The distance warning function cannot
take into account road, weather or traffic con-
ditions. The distance warning function is only
an aid. You are responsible for the distance to
the vehicle in front, for vehicle speed, braking
in good time and for staying in your lane.
Following damage to the front end of the vehi-
cle, have the configuration and operation of
the radar sensor checked at a qualified spe-
cialist workshop. This also applies to collisions
at slow speeds where there is no visible dam-
age to the front of the vehicle.
If you change wheel size, make sure they cor-
respond to the correct wheel size category
(Y page
278). If the category is changed with-
out recoding the control units in the vehicle,
the functioning of the distance warning feature
may be impaired. COLLISION PREVENTION
ASSIST may then detect a malfunction and
switch itself off.
Operation
X To activate/deactivate: activate or deacti-
vate the distance warning function in the on-
board computer

(Y page 190).
If the distance warning function of COLLI-
SION PREVENTION ASSIST is activated, the
display shows the Ä symbol:
R in the header
R in the Status Overview of the Assist.
menu (Y page 189)
At speeds up to approx 20 mph (30 km/h)
the display in vehicles with Active Parking
Assist first shows the í status indicator.
Only from a speed of about 20 mph
(30 km/h) does the display show the
Äsymbol instead of the í status indica-
tor.
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. With the help of the radar sensor sys-
tem, the distance warning function can detect
obstacles that are in the path of your vehicle
for an extended period of time. If the distance
warning function detects that there is a risk of
a collision, you will be warned visually and,
where necessary, acoustically. Without your intervention, the distance warning function
cannot prevent a collision.
The distance warning function issues a warn-
ing at speeds:
R from about

4 mph (7 km/h) if you approach
a vehicle traveling in front or a stationary
vehicle too quickly. The · warning lamp
in the instrument cluster then lights up and
an intermittent warning tone also sounds.
At speeds up to about 45 mph (70 km/h),
the system also detects stationary obsta-
cles, for example stopped or parked vehi-
cles.
X Brake immediately until the distance from
the obstacle increases and the risk of a
front-end collision passes.
or X Take evasive action, provided it is safe to do
so.
Adaptive Brake Assist General notes
Adaptive Brake Assist evaluates the traffic sit-
uation with the help of the radar sensor sys-
tem and can detect obstacles which have been
in your vehicle's path for an extended period
of time. From speeds above 4 mph (7 km/h

),
Adaptive Brake Assist aids you in braking dur-
ing hazardous situations.
Up to a speed of approximately 125 mph
(200 km/h), Adaptive Brake Assist is capable
of reacting to moving obstacles that have
already been detected as such at least once
over the period of observation.
Important safety notes G
WARNING
Adaptive Brake Assist does not react:
R to people or animals
R to oncoming vehicles
R to crossing traffic
R to stationary obstacles
R when cornering
As a result, the Adaptive Brake Assist may
not intervene in all critical conditions. There
is a risk of an accident. 150
Driving systems
Driving and parking

Always pay careful attention to the traffic
situation and be ready to brake. G
WARNING
Adaptive Brake Assist cannot always clearly
identify objects and complex traffic situa-
tions.
In such cases, Adaptive Brake Assist can:
R intervene unnecessarily
R not intervene
There is a risk of an accident.
Always pay careful attention to the traffic
situation and be ready to brake. Terminate
the intervention in a non-critical driving sit-
uation.
In particular, the detection of obstacles can be
impaired in the case of:
R dirt on the sensors or anything else covering
the sensors
R snow or heavy rain
R interference from other radar sources
R 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
Due to the nature of the system, particularly
complicated but non-critical driving conditions
may also cause Adaptive Brake Assist to inter-
vene.
If you fail to adapt your driving style, Adaptive
Brake Assist can neither reduce the risk of
accident nor override the laws of physics.
Adaptive Brake Assist cannot take into
account road, weather or traffic conditions.
Adaptive Brake Assist is only an aid. You are
responsible for the distance to the vehicle in
front, for vehicle speed, braking in good time
and for staying in your lane.
Following damage to the front end of the vehi-
cle, have the configuration and operation of
the radar sensor checked at a qualified spe-
cialist workshop. This also applies to collisions
at slow speeds where there is no visible dam-
age to the front of the vehicle.
If you change wheel size, make sure they cor-
respond to the correct wheel size category
(Y page
278). If the category is changed with- out recoding the control units in the vehicle,
the functioning of Adaptive Brake Assist may
be impaired. COLLISION PREVENTION ASSIST
may then detect a malfunction and switch
itself off.
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.
Operation With the help of the radar sensor system,
Adaptive Brake Assist can detect obstacles
that have been in the path of your vehicle for
an extended period of time. Adaptive Brake
Assist does not react to stationary obstacles.
If Adaptive Brake Assist detects a risk of colli-
sion with a vehicle traveling in front or with a
stationary obstacle, the system calculates the
braking force necessary to avoid this collision.
If you apply the brakes forcefully, Adaptive
Brake Assist will automatically increase the
braking force to a level suitable for the traffic
conditions.
X Brake until the distance to the obstacle
increases and the risk of a collision passes.
ABS prevents the wheels from locking.
The brakes function as usual again if:
R you release the brake pedal
R there is no longer any danger of a collision
R no obstacle is detected in front of your vehi-
cle
Braking assistance is then ended. Blind Spot Assist
General notes Blind Spot Assist monitors the areas on either
side of the vehicle that are not visible to the
driver with two lateral, rear-facing radar sen-
sors in the bumper. It supports you from
speeds of approximately

20 mph (30 km/h). A
warning display in the exterior mirrors draws
your attention to vehicles detected in the
monitored area. If you then switch on the cor-
responding turn signal to change lane, you will
also receive an optical and audible collision
warning. Driving systems
151
Driving and parking Z

For vehicles with steering wheel buttons you
can have the current ATTENTION ASSIST
(Attention Level) assessment displayed.
X Select Status Overview in the Assist.
menu and display the attention level
(Y page
189).
The following information is displayed: R the length of the journey since the last
break.
R the attention level determined by ATTEN-
TION ASSIST, displayed in a bar display in
five levels from low to high.
R if ATTENTION ASSIST is unable to calculate
the attention level and cannot output a
warning, the System Passive message
appears in the display. The bar display is
then dimmed. This is the case, for example,
if you are predominantly driving at a speed
below

40 mph (60 km/h) or above 125 mph
(200 km/h).
Activating ATTENTION ASSIST X
Activating ATTENTION ASSIST with the on-
board computer:
R on vehicles without steering wheel but-
tons

(Y page 180)
R on vehicles with steering wheel buttons
(Y page 190)
For vehicles with steering wheel buttons,
the system determines the attention level of
the driver depending on the setting selec-
ted:
Standard: the sensitivity with which the
system determines the attention level is set
to normal.
Sensitive: the sensitivity is set higher. The
driver is warned earlier.
When ATTENTION ASSIST is switched on and
the vehicle engine is running: R on vehicles without steering wheel buttons,
the À indicator lamp in the instrument
cluster lights up
R on vehicles with steering-wheel buttons, the
display shows the À symbol:
- in the status area
- in the Status Overview of the Assist.
menu (Y page

189)
For vehicles with steering wheel buttons, if you
deactivate ATTENTION ASSIST, the system is
automatically re-activated when you start the engine. The system sensitivity then corre-
sponds to the last selection activated – stand-
ard or sensitive.
If you switch off ATTENTION ASSIST in a vehi-
cle without steering wheel buttons, the system
remains switched off even after you start the
engine. The status of the system after switch-
ing on the engine always corresponds to the
status last selected.
Warning in the display If the system detects tiredness or increasing
lapses in concentration, the warning
Atten‐
tion Assist: Take a Break! or Attent.
Asst: Take Break!is shown in the display.
An additional warning tone sounds.
X If necessary, take a break.
X Confirm the message by pressing the a
button on the steering wheel.
On long journeys, take regular breaks in good
time to allow yourself to rest. If you do not
take a break and ATTENTION ASSIST contin-
ues to detect increasing lapses in concentra-
tion, you will be warned again after

15 minutes
at the earliest. This will only happen if ATTEN-
TION ASSIST still detects typical indicators of
fatigue or increasing lapses in concentration. PARKTRONIC
General notes PARKTRONIC is an electronic parking aid. The
system is equipped with ultrasonic sensors in
the front and rear bumpers to monitor the area
around your vehicle. PARKTRONIC indicates
visually and audibly the distance between your
vehicle and an object.
Your vehicle features two separate sound
emitters with different frequencies for the
warning tones. The warning ranges in front of
and behind the vehicle are indicated by differ-
ent warning tones.
PARKTRONIC is activated automatically when
you:
R turn the key to position 2 in the ignition lock
R release the parking brake and
R move the selector lever to position D, N or R156
Driving systems
Driving and parking

PARKTRONIC is deactivated at speeds above
11 mph (18 km/h
). PARKTRONIC is reactiva-
ted at speeds below 10 mph (16 km/h).
Important safety notes PARKTRONIC is only an aid. It cannot replace
your own awareness of the immediate sur-
roundings. You are responsible for safe
maneuvering, parking and pulling away. Make
sure that there are no persons, animals or
objects in the maneuvering area while maneu-
vering and parking in/leaving parking spaces.
! Pay particular attention to obstacles above
or below the sensors when parking, such as
flower pots or trailer towbars. PARKTRONIC
does not recognize such objects when they
are in the immediate vicinity of the vehicle.
You could damage the vehicle or objects.
PARKTRONIC can suffer interference from:
R ultrasonic sources such as a truck's
compressed-air brakes, an automatic car
wash or a pneumatic drill
R attachments to the vehicle, e.g. rear
mounted racks
R number plates (vehicle license plates)
that are not affixed flat against the
bumper
R dirty or icy sensors
Remove a detachable trailer coupling if it is no
longer required. PARKTRONIC measures the
minimum detection range to an obstacle from
the bumper, not the ball coupling.
Range of the sensors PARKTRONIC does not account for obstacles
that are:
R beneath its detection range, e.g. persons,
animals or objects
R above its detection range, e.g. overhanging
loads, overhangs or loading ramps of trucks The sensors must be free of dirt, ice or slush.
Otherwise, they cannot function correctly.
Clean the sensors regularly, taking care not to
scratch or damage them (Y page

267).
Front sensors Center Approx. 39 in
(100 cm

) Corners Approx. 24 in
(60 cm

) Rear sensors
Center Approx. 47 in
(120 cm

) Corners Approx. 31 in
(80 cm

) Minimum distance
Center Approx. 8 in (20 cm)
Corners Approx. 8 in (20 cm)
If an obstacle is within this range, the corre-
sponding segments of the warning displays
light up and you hear a warning tone. If the
distance falls below the minimum, the dis- Driving systems
157
Driving and parking Z

Towing a trailer
PARKTRONIC detects a coupled trailer if your
vehicle is equipped with the corresponding
electrical installations for trailer towing.
PARKTRONIC is deactivated for the rear area
when you establish an electrical connection
between your vehicle and a trailer. If you use
an adapter for the socket, remove it from the
socket after detaching the trailer. Otherwise,
PARKTRONIC remains deactivated for the rear
area.
Problems with PARKTRONIC Problem
Possible causes/consequences and
M SolutionsOnly the red segments
in the PARKTRONIC
warning displays are lit.
In addition, a warning
tone sounds for approx.
two seconds
PARKTRONIC is then
deactivated.
The indicator lamp of
the f button lights
up and the red seg-
ments in the
PARKTRONIC warning
display go out. PARKTRONIC has malfunctioned and has switched itself off.
X
If problems persist, have PARKTRONIC checked at a qualified
specialist workshop. The PARKTRONIC warn-
ing displays implausible
distances.
For example, all the
segments may be lit
even though there is no
obstacle present. The PARKTRONIC sensors are dirty or iced up.
X Clean the PARKTRONIC sensors ( Y page 267).
X Turn the key to position 2 in the ignition lock. The license plate or other parts attached near the sensors may not
be secured correctly.
X Check the license plate and attachment parts near the sensors
for correct seating. An external radio or ultrasonic source may be causing interference.
X Check PARKTRONIC functions in a different location. Active Parking Assist
General notes Active Parking Assist is an electronic parking
aid. The system uses ultrasound sensors to
measure the road on both sides of the vehicle
and indicates suitable parking spaces. It can
then actively steer and brake the vehicle to
help you to park and exit the parking space.
Active Parking Assist includes the
PARKTRONIC parking aid which indicates visu-
ally and audibly the distance between your vehicle and an obstruction. To do this,
PARKTRONIC uses the ultrasonic sensors of
the Active Parking Assist

(Y page 156).
Important safety notes Active Parking Assist is only an aid. It is not a
substitute for your attention to the immediate
surroundings. You are responsible for safe
maneuvering, parking and pulling away. Make
sure that no persons, animals or objects are in
the maneuvering range. Driving systems
159
Driving and parking Z