ECU MERCEDES-BENZ A-CLASS HATCHBACK 2021 Workshop Manual

HOLD function
HOLD function
HOLD function
HOLD function
The HOLD function holds
theve hicle at a stand-
still without requ iring youto depress the brake
pedal, e.g. while waiting in tra1c.
The HOLD function is only an aid. The responsibil-
ity forth eve hicle safely standing still remains with
th e driver.
Syst
Syst em limits em limits
The HOLD function is only intended toprov ide
assistance when driving and is not a su1cient
means of safeguarding theve hicle against rolling
awa y when stationa ry.
R The incline must not be greater than 30%. A
A ctiv ctiv ating/deactiv
ating/deactiv ating t
ating the HOLD function
he HOLD function &
W
WARNING
ARNING Risk of an accident due tothe
HOLD function being active when you
lea vetheve hicle
If th eve hicle is only braked with the HOLD
function it could, in thefo llowing situations,
ro llawa y:
R Ifth ere is a malfunction in the system or in
th e po wer suppl y.
R Ifth e HOLD function is deactivated by
depressing the accelerator pedal or brake
pedal, e.g. byave hicle occupant. #
Always secure theve hicle against rolling
awa y before you lea veit. R
R
eq
eq uir
uir ements:
ements:
R The vehicle is stationar y.
R The driver's door is closed or the seat belt on
th e driver's side is fastened.
R The vehicle has been star ted or has been
automatically switched o. bythe ECO start/
stop function. R
The vehicle has been star ted.
R The electric parking brake is released.
R Active Distance Assist DISTRONIC is deactiva-
te d.
R V
V ehicles wit
ehicles wit h aut
h automatic tr
omatic tr ansmission:
ansmission: the
transmission is in position h,kori.
A
A ctiv
ctiv ating t
ating t he HOLD function
he HOLD function #
Depress the brake pedal, and aTer a short
time quickly depress fur ther until theë
display appears in the Instrument Displa y. #
Release the brake pedal.
Deactiv
Deactiv ating t
ating the HOLD function
he HOLD function #
Depress the accelerator pedal topull away.
or #
Depress the brake pedal until theë display
disappears from the Instrument Displa y.
The HOLD function is deactivated in thefo llowing
situations:
R Active Distance Assist DISTRONIC is acti va-
te d. Driving and parking
225
225

R
V
Vehicles wit
ehicles wit h aut
h automatic tr
omatic tr ansmission:
ansmission: the
transmission is shiTed toposition j.
R The vehicle is secured with the electric par k-
ing brake.
In thefo llowing situations, theve hicle is held by
transmission position jand/or bythe electric
parking brake:
R The seat belt is unfastened and the driver's
door is opened.
R The vehicle is switched o..
R There is a system malfunction.
R The po wer supply is insu1cient.
V
V ehicles wit ehicles wit h manual tr
h manual tr ansmission
ansmission
The Brake immediately message may also appear
in the Instrument Displa y:#
Immediately depress the brake pedal /rmly
until thewa rning message disappears.
The HOLD function is deactivated.
A horn sounds at regular inter vals if, despite the
Brake immediately message,you switch o. the
ve hicle, remo veyour seat belt and open the driv-
er's door. If you attem pttolock theve hicle, the horn
tone becomes louder. The vehicle cann otbe
loc ked until you ha vedeactivated the HOLD func-
tion.
% Once you ha veswitched o. theve hicle, you
cannot restart it until you ha vedeactivated
th e HOLD function. F
F
unction of Hill St
unction of Hill Star
art Assist
t Assist Hill
Start Assist holds theve hicle for a short time
when pulling away on a hill under thefo llowing
conditions:
R V
Vehicles wit
ehicles wit h aut
h automatic tr
omatic tr ansmission:
ansmission: the
transmission is in position hork.
R The electric parking brake is released.
This gives you enough time tomo veyour foot
from the brake pedal tothe accelerator pedal and
depress it before theve hicle begins torollaw ay. &
W
WARNI NG
ARNI NGRisk of accident and injury due
to theve hicle rolling away
ATer a sho rttime, Hill Start Assist no lon ger
holds theve hicle. #
SwiTly mo veyour foot from the brake
pedal tothe accelerator pedal. Do not
lea vetheve hicle when it is being held by
Hill Start Assist. F
F
unction of A
unction of A dap
daptiv
tive Br
e Br ak
ake Lights
e Lights Ad
aptive Brake Lights warnfollowing tra1c in an
emer gency braking situation with thefo llowing
actions:
R By 0ashing the brake lamps
R By activating the hazard warning lights
If th eve hicle is braked sharply from speeds abo ve
50 km/h, the brake lamps 0ash rapidl y.This pro-
vides tra1c tr avelling behind you with an even
more noticeable warning.
If th eve hicle is tr avelling at speeds of more than
70 km/h at the beginning of the brake applica-
tion, the hazard warning lights switch on once the
ve hicle is stationar y.When you pull away again,
th e hazard warning lights will switch o. automati-
cally at appr oximately 10 km/h. You can also 226
226
Driving and parking

switch o.
the hazard warning lights using the haz-
ard warning button. S
S
t
tar
ar t-o.
t-o. assist
assist F
F
unction of t
unction of t he
hest
star
ar t-o.
t-o. assist
assist
The start-o. assist enables optimal vehicle accel-
eration from a standstill. Forth is, a suitably high-
gr ip road sur face is requ ired, the tyres and vehicle
must also be in good condition.
Do not activate the start-o. assist on public
ro ads.
Be sure toobser vethe saf ety no tes and informa-
tion on ESP ®
(/ page 222).
A
A ctiv ctiv ating t
ating t he
hest
starar t-o.
t-o. assist
assist &
W WARNING ARNING Risk of skidding and having an
accident from wheels spinning
When you use start-o. assist, individual
wheels could spin and you could lose control
of theve hicle.
If ESP ®
is deactivated, there is a risk of skid-
ding and accident! #
Make sure that no persons or obs tacles
are in the close vicinity of your vehicle. #
Deactivating ESP ®
(/ page 224). #
Movethe steering wheel tothe straight-ahead
position. #
Depress the brake pedal /rmly with your leT
fo ot and keep it depressed. #
Engage theh drive position (/ page 185). #
Select the sportiest available drive prog ram
B orC(/ page 179). #
Rapidly depress the accelerator pedal full y. #
Take your foot o. the brake, but keep the
accelerator pedal depressed.
The vehicle pulls away at maximum accelera-
tion. #
Switch on ESP ®
once the acceleration proce-
dure is comple te. ESP ®
will otherwise not be
able tostabilise theve hicle if theve hicle
starts toskid or a wheel starts tospin.
Cancelling t Cancelling t he
hest
star
ar t-o.
t-o. assist
assist #
Remo veyour foot from the accelerator pedal. #
Reactivate the ESP ®
. A
A
TTENTION ASSIST
TTENTION ASSIST F
F
unction of A
unction of A TTENTION ASSIST
TTENTION ASSIST
AT TENTION ASSIST assists you on long, mono to-
nous journe ys, e.g. on mo torw ays and trunk
ro ads. If ATTENTION ASSIST de tects indicators of
fa tigue or increasing lapses in concentration on
th e part of the driver, it suggests taking a break.
AT TENTION ASSIST is only an aid. It cannot
alw ays de tect fatigue or lapses in concentration in
time. The system is not a substitute for a well-res-
te d and attentive driver. On long journe ys,ta ke
re gular breaks in good time that allow for ade-
qu ate recuperation.
Yo u can choose between two settings:
R St
Standar
andar d:
d:normal system sensitivity.
R Sensitiv
Sensitiv e:
e:higher system sensitivity. The driver
is wa rned earlier and the attention le vel de tec-
te dby ATTENTION ASSIST is ada pted accord-
ingl y.
If dr owsiness or increasing lapses in concent ra-
tion are de tected, theATTENTION ASSIST: Take Driving and parking
227
227

&
W
WARNI NG
ARNI NGRisk of an accident due to
Ac tive Distance Assist DISTRONIC being
acti vewhen you lea vethe driver's seat
If yo u lea vethe driver's seat while theve hicle
is being braked byActive Distance Assist
DISTRONIC onl y,theve hicle can rollaw ay. #
Always deacti vate Ac tive Distance Assist
DISTRONIC and secure theve hicle to
pr ev ent it from rolling away before you
lea vethe driver's seat. #
Select Owiththe leT rock er switch.
% Ifyo u brake, deactivate ESP ®
or if ESP ®
inter-
ve nes, Active Distance Assist DISTRONIC is
deactivated.
Incr
Incr easing/decr
easing/decr easing t
easing the st
he stor
ored speed
ed speed #
1 km/h: press roc ker switch 1upM or
down Ntothe pressure point, or press and
hold (increments of 1 km/h).
or #
10 km/h: press rock er switch 1upM or
down Nbeyond the pressure point, or
press and hold (increments of 10 km/h).
or #
Accelerate theve hicle tothe desired speed
and press rock er switch 1upM.
Changing t
Changing t he
hespeci/ed
speci/ed dist
distance t
ance t o t
o the v
he v ehicle in
ehicle in
fr
fr ont
ont #
T
To r
o r educe t
educe t he
hespeci/ed
speci/ed dist
distance:
ance: pressthe
ri ght rock er switch up ( Ñ). #
T To incr o incr ease t
ease t he
hespeci/ed
speci/ed dist
distance:
ance: pressthe
ri ght rock er switch down ( Ò).
F
F unction of A
unction of A ctiv
ctive Speed Limit Assist
e Speed Limit Assist
If a change in the speed limit of 20 km/h or more
is de tected and automatic adoption of speed lim-
its is activated, the new speed limit is automati-
cally adop ted as the stored speed (/ page 249).
The driven speed is adjusted when theve hicle is
le ve l with the tra1c sign at the latest. In the case
of signs indicating entry into an urban area, the
speed is adap ted according tothe speed permit-
te d within the urban area. The speed limit display in
the Instrument Display is alw ays updated when
th eve hicle is le vel with the tra1c sign.
If th ere is no speed restriction on an unlimited
str etch ofroad (e.g. on a mo torw ay),th ere com-
mended speed is automatical lyadop ted as the
stored speed. The system uses the speed stored
on an unlimited str etch ofroad as there commen-
ded speed. If you do not alter the stored speed on
an unlimited str etch ofroad, there commended
speed is 130 km/h.
If Ac tive Distance Assist DISTRONIC has been put
into passive mode bypressing the accelerator
pedal, only speed limits which are higher than the
set speed are adop ted.
Obser vethe no tes on driving systems and your
re sponsibility; you may otherwise failto recognise
dangers (/ page 219).
Syst
Syst em limits em limits
The system limits of Tra1c Sign Assist apply to
th e de tection of tra1c signs (/ page 247).
Speed limits below 20 km/h are not automatical ly
adop tedby the system as the stored speed. Tem-
porary speed restrictions (e.g. for a cer tain time
or due towe ather conditions) cann otbe proper ly 236
236
Driving and parking

to
ne sounds in addition tothe visual warning mes-
sage.
If th e driver still does not respond tothewa rning,
th eBeginning emergency stop message appears
in the Instrument Displa y.Ifth e driver still does
not respond, Active Distance Assist DISTRONIC
re duces the speed. The vehicle is decelerated in
stages toa standstill.
Depending on the countr y,at speeds below
60 km/h the hazard warning lights switch on
automaticall y.
When theve hicle is stationar y,thefo llowing
actions are car ried out:
R The vehicle is secured with the electric par k-
ing brake.
R Active Distance Assist DISTRONIC is ended.
R The vehicle is unloc ked.
R If possible, an emer gency call is placed tothe
Mercedes-Benz eme rgency call centre.
The driver can cancel the deceleration at any time
by per form ing one of thefo llowing actions:
R Steering R
Braking or accelerating
R Deactivating Active Distance Assist
DISTRONIC A A
ctiv
ctiv e Br
e Br ak
ake Assist
e Assist F
F
unction of A
unction of A ctiv
ctive Br
e Br ak
ake Assist
e Assist
Ac tive Brake Assist consists of thefo llowing func-
tions:
R Distance warning function
R Autonomous braking function
R Situation-dependent braking assistance
R V
Vehicles wit
ehicles wit h Dr
h Driving Assist
iving Assist ance P
ance Pack
ackag
age:
e: Eva-
sive Steering Assist and cornering function
Ac tive Brake Assist can help youto minimise the
ri sk of a collision with vehicles, cyclists or pedes-
trians or toreduce the e.ects of such a collision.
If Ac tive Brake Assist has de tected a risk of colli-
sion, a warning tone sounds and theL dis-
ta nce warning lamp lights up in the inst rument
cluster. V V
ehicles wit ehicles wit h PRE-S
h PRE-SAFE
AFE®
®
:
:depending on the coun-
tr y, an additional haptic warning occurs in the
fo rm of slight, repeated tensioning of the seat
belt.
If yo u do not react tothewa rning, autonomous
braking can be initiated in critical situations.
In especially critical situations, Active Brake Assist
can initiate autonomous braking directl y.In this
case, thewa rning lamp and warning tone occur
simultaneously with the braking application.
If yo u apply the brake yourself in a critical situa-
tion or apply the brake during autonomous brak-
ing, situation-dependent braking assistance
occurs. The brake pressure increases up tomaxi-
mum full-s top braking if necessar y.
Obser vethe no tes on driving systems and your
re sponsibility; you may otherwise failto recognise
dangers (/ page 219). Driving and parking
241 241

Do not
exceed thefo llowing values:
R Perm issible towing capacity
R Perm issible rear axle load of theto wing vehi-
cle
R Perm issible gross weight of theto wing vehicle
R Perm issible gross weight of the trailer
R Maximum permissible speed of the trailer
Ensure thefo llowing before starting a journe y:
R The tyre pressure on there ar axle of theto w-
ing vehicle is set for a maximum load
R The lighting of the connected trailer is opera-
tional
R V
V ehicles wit
ehicles wit hout LED headlam
hout LED headlam ps or MUL
ps or MULTI-
TI-
BEAM LED headlam
BEAM LED headlam ps:
ps:the headlamps ha ve
been set cor rectly
In theev ent of increased rear axle load, the car/
trailer combination must not exceed a maximum
speed of 100 km/h forre asons conce rning the
operating permit. This also applies in countries in
which the permissible maximum speed for car/
trailer combinations is abo ve100 km/h. F
F
olding t
olding t he ball nec
he ball nec k out and in
k out and in &
W
WARNING
ARNING Risk of accident due tothe ball
neck not being engaged
If th e ball neck is not engaged, the trailer may
come loose. #
Always engage the ball neck as descri-
bed. &
W
WARNING
ARNING Risk of injury from ball neck
swinging outwards
The ball neck may swing outwards when
unlocking or when it has not been proper ly
engaged.
There is a risk of injury within the ball neck's
ra nge of mo vement! #
Unlock the ball neck only when its range
of mo vement is unobstructed. #
Always be sure the ball neck is engaged
when folding in wards. *
N NOOTE
TE Increased risk of damage toprop-
erty due tofolded-out ball neck #
When the trailer is not coupled or the
bicycle rack is attached, fold in the ball
neck or, in the case of a fully electric
trailer hitch, retract the ball nec k. *
N
NO
OTE
TE Damage totheve hicle due toincor-
re ct use of the trailer hitch When a trailer hitch is used
toreco ver a vehi-
cle, theve hicle may be damaged in the proc-
ess. #
Use the trailer hitch only for pulling a
trailer or attaching appr oved car rier sys-
te ms (e.g. a bicycle rack ). R
R
eq
eq uir
uir ements:
ements:
R The vehicle is secured against rolling away.
R The swivel range is clear.
R The trailer cables or ada pter plugs ha vebeen
re mo ved. Driving and parking
271
271

F
F
olding t
olding t he ball nec
he ball nec k out
k out #
Pull switch 2until the ball neck unloc ks.
The ball neck will fold out from under there ar
bumper.
Indicator lamp 1will 0ash. #
Pull the ball neck in the direction of the ar row
until it engages audibly in a vertical position.
Indicator lamp 1onthe ball neck release
switch will go out.
If th e ball neck is not securely loc ked in place,
th eTrailer coupling Check lockmessage will
appear on the inst rument displa y. #
Remo vethe co ver cap from the ball head and
store it in a safe place. Make sure
that the ball on the ball neck is clean.
Check that it is either greased or dry (g rease-
free), depending on the inst ructions forth e trailer.
F
F olding t olding t he ball nec
he ball nec k in
k in #
Pull switch 2until the ball neck unloc ks.
The ball neck will fold up under there ar
bumper.
Indicator lamp 1will 0ash. #
Push the ball neck in the direction of the
ar ro w until it engages audibly behind the
bumper.
Indicator lamp 1will go out and the message
on the inst rument display will disappear.
Obser vethe information about the displa yson the
inst rument cluster:
R Indicator and warning lamps (/ page 476)
R Display message s (/page 409) Coupling up/uncoupling a tr Coupling up/uncoupling a tr
ailer
ailer R
R
eq
eq uir
uir ements:
ements:
R The ball neck is extended and engaged in a
securely loc ked position. 272
272
Driving and parking

Tr
ailers with a 7-pin plug can be connected tothe
ve hicle with thefo llowing adap ters:
R Adapter plug
R Adapter cable
The trailer will be cor rectly de tected bytheve hi-
cle only if thefo llowing conditions are met:
R The trailer is connected cor rectl y.
R The trailer lighting system is in working order.
The functions of thefo llowing systems will be
a.ec tedbya cor rectly connected trailer:
R ESP ®
trailer stabilisation
R Active Lane Keeping Assist
R Parking Assist PARKTRONIC
R Active Parking Assist
R Blind Spot Assist or Active Blind Spot Assist
R Drive Away Assist
R Cross Tra1c Ale rt
R Reversing camera
R 360° Camera Coupling up a tr
Coupling up a tr ailer
ailer
* NO
NOTE
TEDamage tothe star ter battery due
to full dis charge Charging
the trailer battery using the po wer
supply of the trailer can damage the star ter
batter y. #
Do not use theve hicle's po wer supply to
ch arge the trailer batter y. #
Remo vethe co ver cap from the ball head and
store it in a safe place. #
Position the trailer on a le vel sur face behind
th eve hicle and couple it up totheve hicle. #
Open the soc ket cap. #
Inse rtthe plug with lug 1ingroo ve 3 on
th e soc ket. #
Turn bayonet coupling 2totheright as far as
it will go. #
Let the cap engage. #
Secure the cable tothe trailer with cable ties
(only if you are using an adap ter cable). #
Make sure that the cable is alw ays slack for
ease of mo vement during cornering.
Under thefo llowing conditions, a message may
appear on the inst rument display even if the
trailer has been connec ted cor rectl y:
R LEDs ha vebeen ins talled in the trailer lighting
system.
R The cur rent has fallen below the trailer lighting
system's minimum cur rent (50 mA).
% Accessories can be connected tothe perma-
nent po wer supply up to180 W and tothe
po we r supply that is switched on via the igni-
tion loc k. Driving and parking
273
273

U
U
ncoupling a tr
ncoupling a tr ailer
ailer &
W
WARNI NG
ARNI NGRisk of being crushed and
becoming trapped when uncoupling a
trailer
When uncoupling a trailer with an engaged
inertia-activated brake, your hand may
become trapped between theve hicle and the
trailer dr awbar. #
Do not uncouple trailers with an engaged
ove rrun brake. *
N
NOOTE
TE Damage during uncoupling with an
engaged overrun brake The
vehicle may be damaged if you uncouple
with an engaged overrun brake. #
Do not uncouple trailers with an engaged
ove rrun brake. #
Secure the trailer against rolling away. #
Disconnect the electrical connection between
th eve hicle and the trailer. #
Uncouple the trailer. #
Place the co ver cap on the ball head.
% T
Tr
railer
ailer s wit
s wit h LED lighting:
h LED lighting: aTer uncoupling the
traile r,switch theve hicle on and then o.
again. Bicy
Bicy
cle r
cle r ac
ack function
k function &
W
WARNING
ARNING Risk of an accident if the bicy-
cle rack is used incor rectly
The bicycle rack may become de tach ed from
th eve hicle in thefo llowing cases:
R the permissible load capacity of the trailer
hitch is exceeded.
R the bicycle rack is used incor rectl y.
R the bicycle rack is secured tothe ball neck
beneath the ball head.
Obser vethefo llowing foryo ur ow n sa fety and
th at of other road users:
R always adhere tothe permissible load
capacity of the trailer hitch. R
always obser vethe permissible rear axle
load of theto wing vehicle.
R use the bicycle rack only totransport bicy-
cles.
R always proper lysecure the bicycle rack by
attaching it tothe ball head.
R use only bicycle rack s appr ovedby
Mercedes-Benz.
R always obser vethe bicycle rack operating
instructions. *
N NOOTE TE Damage toor breakage of the trailer
hitch due tounsuitable or improper lyused
bicycle rack. #
Only use bicycle rack s appr ovedby
Mercedes-Benz prope rly as described
bel ow. *
N
NO
O TE
TE Increased risk of damage toprop-
erty due tofolded-out ball neck #
When the trailer is not coupled or the
bicycle rack is attached, fold in the ball 274
274
Driving and parking

neck or, in
the case of a fully electric
trailer hitch, retract the ball nec k. Depending on
the bicycle rack 's design, up to
th re e bicycles can be transpor ted on the bicycle
ra ck.
When mounted byattaching toball head 1,the
maximum load capacity is 75 kg. The maximum load capacity is calculated from
the
we ight of the bicycle rack and the bicycle rack
load.
Obser vethe no tes on driving with a roof load,
trailer or fully laden vehicle (/ page 169).
When using a bicycle rack , set the tyre pressure
fo r increased load on there ar axle of theve hicle.
Fu rther information on the tyre pressure can be
fo und in the tyre pressure table (/ page 370).
N
No ot tes on loading
es on loading
The lar gerth e distance between the load's centre
of grav ity and the ball head, thegr eater the load
on the trailer hitch.
Therefore, obser vethefo llowing no tes:
R mount heavy bicycles as close totheve hicle
as possible
R always distribute the load on the bicycle rack
as evenly as possible across theve hicle's lon-
gitudinal axis
Mercedes-Benz recommends removing all de tach-
able parts from bicycles (e.g. bask ets, ch ild seats,
re ch arge able batteries) before loading them onto
th e bicycle rack . This will impr ovethe aerody- namic
resis tance and centre of grav ity of the bicy-
cle rack.
Alw ays secure the bicycles toprev ent them from
moving around and check them at regular inter-
va ls to ensure that they are secure.
Do not use tarp aulins or other co vers. The driving
ch aracteristics and rear view may be impaired. In
addition, aerodynamic resis tance and the load on
th e trailer hitch will increase. Load distribution on
the bicycle rack
1 Vertical distance between centre of grav ity
and ball head Driving and parking
275
275