warning MERCEDES-BENZ B-Class 2017 W246 Service Manual

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. Fully
retract the seat cushion length. 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 lie as flat as possible against the backrest of the
front-passenger seat. The child restraint system must not touch the roof or be subjected to a loadby 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 vehi-
cle belt outlet to the shoulder belt guide on the
child restraint system. The shoulder belt strap
must be routed forwards and downwards from
the vehicle belt outlet. If necessary, adjust the
vehicle belt outlet and the front-passenger seat
accordingly.
Always observe the child restraint system man- ufacturer's installation and operating instruc-
tions. 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 58)
R the rear side windows (Y page 58) 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 transmission out of park position
P.
R start the vehicle's drive system.
They could also operate the vehicle's equip-
ment. 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. Children in the vehicle
57Safety Z

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 work-
ing properly.
X To deactivate: press the child-proof lock
lever down in the direction of arrow 0044.
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 driver's
door. If indicator lamp 0044is off, operation is
possible using the switches in the rear com-
partment. 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 59)
R BAS (Brake AssistSystem) (Y page 59)
R Active Brake Assist (Y page 60)
R ESP ®
(E lectronic StabilityProgram)
(Y page 62)
R EBD (Electronic Brake forceDistribution)
(Y page 63)
R ADAPTIVE BRAKE (Y page 64)
R STEER CONTROL (Y page 64) Important safety notes
If you fail to adapt your driving style or if you are inattentive, the driving safety systems can nei-
ther reduce the risk of an accident nor override
the laws of physics. Driving safety systems are
merely aids designed to assist driving. You are
responsible for maintaining the distance to the 58
Driving safety systemsSafety

vehicle in front, for vehicle speed, for braking in
good time, and for staying in lane. 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.
The driving safety systems described only work
as effectively as possible when there is ade-
quate contact between the tires and the road
surface. Please pay special attention to the
notes on tires, recommended minimum tire
tread depths, etc. (Y page 257).
In wintry driving conditions, always use winter
tires (M+S tires) and if necessary, snow chains.
Only in this way will the driving 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 vehicle 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.
ABS works from a speed of about 5 mph
(8 km/h), regardless of road-surface conditions. ABS works on slippery surfaces, even when you
only brake gently.
Important safety notes i
Observe the "Important safety notes" sec-
tion (Y page 58). 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 193) and dis-play messages which may be shown in the
instrument cluster (Y
page 168).
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 indication
of hazardous road conditions, and functions as a reminder to take extra care while driving. BAS (Brake Assist System)
General information BAS operates in emergency braking situations.
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 58). 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.
Braking X
Keep the brake pedal firmly depressed until
the emergency braking situation is over.
ABS prevents the wheels from locking.
The brakes will function as usual once you
release the brake pedal. BAS is deactivated. Driving safety systems
59Safety Z

Active Brake Assist
General information i
Observe the "Important safety notes" sec-
tion (Y page 58).
Active Brake Assist consists of a distance warn-
ing function with an autonomous braking func-
tion and braking assistance appropriate to the
situation.
Active Brake Assist can help you to minimize the risk of a collision with the vehicle traveling in
front or reduce the effects of such a collision.
If Active Brake Assist detects that there is a risk
of collision, you will be warned visually and
acoustically. If you do not react to the visual and audible collision warning, autonomous braking
can be initiated in critical situations. If you apply
the brake yourself in a critical situation, Adap-
tive Brake Assist supports you with braking
assistance appropriate to the situation.
Important safety notes Detection of hazardous situations can be par-
ticularly impaired by:
R there is dirt on the sensors or anything else
covering the sensors
R there is snow or heavy rain
R there is interference by other radar sources
R there are strong radar reflections, for exam-
ple in parking garages
R a narrow vehicle is traveling in front, e.g. a
motorbike
R a vehicle is traveling in front on a different line
R new vehicles or after servicing is carried out
on the Active Brake Assist system
Observe the important safety notes in the
"Breaking-in notes" section (Y page 108).
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 no visible damage to the front of
the vehicle is apparent.
Activating/deactivating Active Brake Assist is active after every ignition
cycle.
You can activate or deactivate Active Brake
Assist (Y page 162) in the on-board computer. When deactivated, the distance warning func-
tion and the autonomous braking function are
also deactivated.
If Active Brake Assist is deactivated, the 00D4
symbol appears in the assistance graphic dis-
play.
Distance warning function General information
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.
Important safety notesi Observe the "Important safety notes" sec-
tion for driving safety systems (Y page 58). 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 sit-
uation 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 sit-
uation and do not rely solely on the distance
warning function. 60
Driving safety systemsSafety

Function
Starting at a speed of approximately 4 mph
(7 km/h), the distance warning function warns
you if you rapidly approach a vehicle in front. An
intermittent warning tone will then sound, and
the 00BA distance warning lamp will light up in
the instrument cluster.
X Brake immediately in order to increase the
distance from the vehicle in front.
or X Take evasive action, provided it is safe to do
so.
Due to the nature of the system, particularly
complicated but non-critical driving conditions
may also cause the system to display a warning.
With the help of the radar sensor system, the
distance warning function can detect obstacles
that are in the path of your vehicle for an exten-
ded period of time.
Up to a speed of approximately 44 mph
(70 km/ h), the distance warning function can
also react to stationary obstacles, such as stop-
ped or parked vehicles.
Autonomous braking function If the driver does not react to the distance warn-
ing signal in a critical situation, Active Brake
Assist can assist the driver with the autonomous braking function.
The autonomous braking function:
R gives the driver more time to react to critical
driving situations
R can help the driver to avoid an accident or
R reduces the effects of an accident
The autonomous braking function is available in
the following speed ranges:
R 4 - 65 mph (7 - 105 km/ h)for moving objects
R 4 - 31 mph (7 - 50 km/h) for stationary
objects
Due to the nature of the system, particularly
complicated but non-critical driving conditions
may also cause the Autonomous Braking Func-
tion to intervene. Braking assistance appropriate to the
situation General information
i Observe the "Important safety notes" sec-
tion (Y page 58).
With the help of the radar sensor system, Adap- tive Brake Assist can detect obstacles that are in
the path of your vehicle for an extended period
of time.
If Adaptive Brake Assist detects a risk of colli-
sion with the vehicle in front, it calculates the
brake pressure necessary to avoid a collision. If
you apply the brakes forcefully, the braking
assistance adapts to the situation and automat-
ically increases the brake pressure to a degree
appropriate to the traffic situation.
Braking assistance appropriate to the situation
provides braking assistance in hazardous situa- tions at speeds above 4 mph (7 km/h). It uses
radar sensor technology to assess the traffic
situation.
Situation-dependent braking assistance is capa-
ble of reacting to moving objects that have
already been recognized as such at least once
over the period of observation, up to vehicle
speeds of around 155 mph (250 km/h).
Braking assistance appropriate to the situation
can also detect stationary objects, up to vehicle speeds of around 44 mph 70 km/h.
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 collision.
R no obstacle is detected in front of your vehi-
cle.
Braking assistance appropriate to the situation
is then deactivated.
Important safety notes i Observe the "Important safety notes" sec-
tion for driving safety systems (Y page 58). G
WARNING
Adaptive Brake Assist does not react:
R to people or animals
R to oncoming vehicles Driving safety systems
61Safety
Z

R
to crossing traffic
R when cornering
As a result, Adaptive Brake Assist may not
intervene in all critical conditions. There is a
risk of an accident.
Always pay careful attention to the traffic sit- uation 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 might:
R intervene unnecessarily
R not intervene
There is a risk of an accident.
Always pay careful attention to the traffic sit- uation and be ready to brake. Terminate the
intervention in a non-critical driving situation.
Due to the nature of the system, complex but
non-critical driving conditions may also cause
Active Brake Assist to intervene.
Even if Active Brake Assist is not available due to a malfunction in the radar sensor system, the
brake system is still available with full brake
boosting effect and BAS. ESP
®
(Electronic Stability Program)
General notes i
Observe the "Important safety notes" sec-
tion (Y page 58).
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 vehi- cle 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 (Electronic Traction System) i
Observe the "Important safety notes" sec-
tion (Y page 58).
ETS traction control is part of ESP ®
.
Traction control brakes the drive wheels indi-
vidually 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 transfer-
red 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" sec-
tion (Y page 58). G
WARNING
If ESP ®
is malfunctioning, ESP ®
is unable to
stabilize the vehicle. Additionally, further driv- ing safety systems are deactivated. This
increases the risk of skidding and an accident.
Drive on carefully. Have ESP ®
checked at a
qualified specialist workshop.
When towing your vehicle with the front axle
raised, observe the notes on ESP ®
(Y page 253).
When towing the vehicle with the rear axle
raised, observe the notes on ESP ®
(Y page 254).
If the 00BB ESP®
OFF warning lamp lights up
continuously, ESP ®
is deactivated.
If the 00E5 ESP®
warning lamp and the 00BB
warning lamp are lit continuously, ESP ®
is not
available due to a malfunction.
Observe the information on warning lamps
(Y page 195) and display messages which may
be shown in the instrument cluster
(Y page 168).
Only use wheels with the recommended tire
sizes. Only then will ESP ®
function properly. 62
Driving safety systemsSafety

Characteristics of ESP
®General information
If the 00E5 ESP®
warning lamp goes out before
beginning the journey, ESP ®
is automatically
active.
If ESP ®
intervenes, the 00E5ESP®
warning lamp
flashes in the instrument cluster.
If ESP ®
intervenes:
X Do not deactivate ESP ®
under any circum-
stances.
X Only depress the accelerator pedal as far as
necessary when pulling away.
X Adapt your driving style to suit the prevailing
road and weather conditions.
Deactivating/activating ESP ®Important safety notes
i Observe the "Important safety notes" sec-
tion (Y page 58).
You can select between the following states of
ESP ®
:
R ESP ®
is activated.
R ESP ®
is deactivated. G
WARNING
If you deactivate ESP ®
, ESP ®
no longer sta-
bilizes the vehicle. There is an increased risk
of skidding and an accident.
Only deactivate ESP ®
in the situations descri-
bed in the following.
The spinning of the wheels results in a cutting
action for better traction on loose surfaces.
It may be best to deactivate ESP ®
in the follow-
ing situations:
R when using snow chains
R in deep snow
R on sand or gravel
i Activate ESP ®
as soon as the situations
described above no longer apply. ESP ®
will
otherwise not be able to stabilize the vehicle if
the vehicle starts to skid or a wheel starts to
spin. !
Avoid spinning the driven wheels for an
extended period with ESP ®
deactivated. You
could otherwise damage the drivetrain.
Deactivating/activating ESP ®
You can deactivate or activate ESP ®
via the on-
board computer (Y page 162).
ESP ®
deactivated:
The 00BB ESP®
OFF warning lamp in the instru-
ment cluster lights up.
ESP ®
activated:
The 00BB ESP®
OFF warning lamp in the instru-
ment cluster goes out.
Characteristics when ESP ®
is deactivated
If ESP ®
is deactivated and one or more wheels
start to spin, the 00E5ESP®
warning lamp in the
instrument cluster flashes. In such situations,
ESP ®
will not stabilize the vehicle.
If you deactivate ESP ®
:
R ESP ®
no longer improves driving stability.
R Engine torque is no longer limited and the
drive wheels are able to spin.
R Traction control is still activated.
R STEER CONTROL is no longer active
R ESP ®
still provides support when you brake
firmly. EBD (electronic brake force distribu-
tion)
General information EBD monitors and controls the brake pressure
on the rear wheels to improve driving stability
while braking.
Important safety notes i
Observe the "Important safety notes" sec-
tion (Y page 58). G
WARNING
If EBD is malfunctioning, the rear wheels can
lock, e.g. under full braking. This increases the risk of skidding and an accident.
You should therefore adapt your driving style
to the different handling characteristics. Have Driving safety systems
63Safety
Z

the brake system checked at a qualified spe-
cialist workshop.
Observe information regarding indicator and
warning lamps (Y page 193) as well as display
messages (Y page 170). ADAPTIVE BRAKE
ADAPTIVE BRAKE enhances braking safety and
offers increased braking comfort. In addition to
the braking function, ADAPTIVE BRAKE also has
the HOLD function (Y page 138) and hill start
assist (Y page 111). STEER CONTROL
General information STEER CONTROL helps you by transmitting a
noticeable steering force to the steering wheel
in the direction required for vehicle stabilization.
This steering assistance is provided in particular if:
R both right wheels or both left wheels are on a
wet or slippery road surface when you brake
R the vehicle begins to skid
Important safety notes i
Observe the "Important safety notes" sec-
tion (Y page 58).
No steering assistance is provided from STEER
CONTROL, if:
R ESP ®
is malfunctioning
R the steering is malfunctioning
If ESP ®
is malfunctioning, you will be assisted
further by the electrical power steering. Recuperative Brake System
G
WARNING
In the event of malfunctions in the Recupera- tive Brake System, the following may occur: R
the braking performance of the electric
motor may be either reduced or not effec-
tive
R brake pedal resistance may be lower than
usual
R pedal travel may be longer than usual
If you do not make an additional effort to apply the brake yourself, the braking effect may not
be sufficient. There is a risk of an accident.
In the event of this malfunction, continue to
depress the brake pedal. The brake system is
still fully functional.
Observe the important safety notes on driving
safety systems (Y page 58).
The Recuperative Brake System converts the
kinetic energy when braking into electrical
energy. The electric motor is used as an alter-
nator during braking. This electrical energy is
then stored in the high-voltage battery.
You can find information about manually adjust- able recuperation under "Steering wheel paddle
shifters" (Y page 115).
If the warning light in the instrument cluster is lit
up, there is a motor malfunction or a brake mal- function.
Observe information regarding indicator and
warning lamps (Y page 192) as well as display
messages (Y page 168). Protection against theft
Immobilizer
The immobilizer prevents your vehicle from
being started without the correct SmartKey.
X To activate with the SmartKey: remove the
SmartKey from the ignition lock.
X To activate with KEYLESS-GO start-func-
tion or KEYLESS-GO: switch the ignition off
and open the driver's door.
X To deactivate: switch on the ignition.
When leaving the vehicle, always take the
SmartKey with you and lock the vehicle. Anyone
can start the drive system if a valid SmartKey
has been left inside the vehicle.
i The immobilizer is always deactivated when
you start the drive system. 64
Protection against theftSafety

SmartKey
Important safety notes
G
WARNING
If children are left unsupervised in the vehicle, they could:
R open the doors, thus endangering other
people or road users.
R get out and disrupt traffic.
R operate the vehicle's equipment.
Additionally, children could set the vehicle in
motion if, for example, they:
R release the parking brake.
R shift the transmission out of park position P
R start the vehicle's drive system.
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 or animals unattended in the
vehicle. Always keep the SmartKey out of
reach of children. G
WARNING
If you attach heavy or large objects to the
SmartKey, the SmartKey could be uninten-
tionally turned in the ignition lock. This could
cause the engine to be switched off. There is a risk of an accident.
Do not attach any heavy or large objects to the
SmartKey. Remove any bulky key rings before
inserting the SmartKey into the ignition lock.
! Keep the SmartKey away from strong mag-
netic fields. Otherwise, the remote control
function could be affected.
Strong magnetic fields can occur in the vicin- ity of powerful electrical installations.
Do not keep the SmartKey: R with electronic devices, e.g. a mobile phone
or another SmartKey.
R with metallic objects, e.g. coins or metal foil.
R inside metallic objects, e.g. a metal case SmartKey functions
0043
0037 To lock the vehicle
0044 0036 To unlock the vehicle
X To unlock centrally: press the0036button.
If you do not open the vehicle within approx-
imately 40 seconds of unlocking:
R the vehicle is locked again.
R anti-theft protection is reactivated.
X To lock: press the 0037button.
The SmartKey centrally locks/unlocks: R the doors
R the tailgate
R the charge socket flap
The turn signals flash once when unlocking and
three times when locking.
When the locator lighting is activated via the
multimedia system, it lights up when it is dark
after the vehicle is unlocked with the remote
control (see the separate operating instruc-
tions).
You can also set an audible signal to confirm
that the vehicle has been locked. The audible
signal can be activated and deactivated using
the on-board computer (Y page 166). KEYLESS-GO
General notes Bear in mind that the drive system can be star-
ted by any of the vehicle occupants if there is a
SmartKey in the vehicle. 66
SmartKeyOpening and closing

approximately six seconds until the battery
check lamp flashes twice (Y page 69).
If the setting of the locking system is changed
within the signal range of the vehicle, pressing
the 0037 or0036 button:
R locks or
R unlocks the vehicle
The SmartKey now functions as follows:
X To unlock: press the0036button once.
X To unlock centrally: press the0036button
twice.
X To lock centrally: press the0037button.
The KEYLESS-GO function is changed as fol-
lows: X To unlock the driver's door: touch the inner
surface of the door handle on the driver's
door.
X To unlock centrally: touch the inner surface
of the door handle on the front-passenger
door or the rear door.
X To lock centrally: touch the outer sensor
surface on one of the door handles.
X To restore the factory settings: press and
hold the 0036and0037 buttons simultane-
ously for approximately six seconds until the
battery check lamp flashes twice
(Y page 69). Mechanical key
General notes If the vehicle can no longer be locked or
unlocked with the SmartKey or KEYLESS-GO,
use the mechanical key.
If you use the mechanical key to unlock and
open the driver's door or the trunk lid, the anti-
theft alarm system will be triggered (Y page 65).
There are several ways to turn off the alarm:
X To deactivate the alarm with the key: press
the 0036 or0037 button on the key.
or X Insert the SmartKey into the ignition lock.
or X To deactivate the alarm with KEYLESS-GO:
press the Start/Stop button in the ignition
lock. The SmartKey must be in the vehicle. or
X Lock or unlock the vehicle using KEYLESS-
GO. The SmartKey must be outside the vehi-
cle.
If you unlock the vehicle using the mechanical
key, the charge socket flap will not be unlocked automatically.
X To unlock the charge socket flap: insert the
SmartKey into the ignition lock.
Removing the mechanical key X
Push release catch 0043in the direction of the
arrow and at the same time remove mechan- ical key 0044from the SmartKey.
For further information about:
R Unlocking the driver's door (Y page 73)
R Unlocking the cargo compartment
(Y page 75)
R Locking the vehicle (Y page 73)
Inserting the mechanical key X
Push mechanical key 0044completely into the
SmartKey until it engages and release
catch 0043is back in its basic position. SmartKey battery
Important safety notes G
WARNING
Batteries contain toxic and corrosive substan- ces. If batteries are swallowed, it can result in
severe health problems. There is a risk of fatal injury. 68
SmartKeyOpening and closing