check engine MERCEDES-BENZ B-CLASS HATCHBACK 2021 Owners Manual

*
N
NO
OTE
TE Damage totheve hicle due todriv-
ing toofast and due toimpacts tothe
ve hicle underbody or suspension compo-
nents In
thefo llowing situations, in particular, there
is a risk of damage totheve hicle:
R theve hicle becomes grounded, e.g. on a
high kerb or an unpa vedro ad
R theve hicle is driven toofast ove r an obsta-
cle, e.g. a kerb, speed bump or po thole
R a heavy object st rike sth e underbody or
suspension components
In situations such as these, damage tothe
body, underbody, suspension components,
wheels or tyres may not be visible. Compo-
nents damaged in this wa y can un expectedly
fa il or, in the case of an accident, may no lon-
ge r absorb there sulting forc e as intended.
If th e underbody panelling is damaged, 0am-
mable materials such as lea ves, grass or twigs
can collect between the underbody and the
underbody panelling. These materials may ignite if
they come into contact with hot parts
of theex haust system. #
Have theve hicle checked and repaired
immediately at a quali/ed specialist
wo rkshop.
or #
If driving saf ety is impaired while con-
tinuing your journe y,pull over and stop
th eve hicle immediatel y,while paying
attention toroad and tra1c conditions,
and contact a quali/ed specialist work-
shop. Plug-in h Plug-in h
ybr
ybr id
id
Hybrid vehicles ha vea combustion engine and an
elect ric mo tor.The energy supply for operating
th eve hicle elect rically is pr ovided bythe high-
vo ltage on-board electrical system. &
D
DAN
AN GER
GER Risk of death and /re due to
modi/ed and/or damaged components of
th e high-voltage on-board electrical sys-
tem
The vehicle's high- voltage on-board electrical
system is under high voltage. If you modify
component parts in theve hicle's high- voltage
on-board electrical system or touch damaged
component parts, you may be electrocuted. In
addition, modi/ed and/or damaged compo-
nents may cause a /re.
In theeve nt of an accident or impact tothe
ve hicle underbod y,components of the high-
vo ltage electrical system may be damaged
although the damage is not visible. #
Never make any modi/cations tothe
high- voltage on-board electrical system. #
Do not switch on or use theve hicle if its
high- voltage on-board electrical system
components ha vebeen modi/ed or dam-
aged. 28 28
General no
tes

#
Neverto uch damaged components of
th e high-voltage on-board electrical sys-
te m. #
ATer an accident, do not touch any com-
ponents of the high-voltage on-board
electrical system. #
ATer an accident, ha vetheve hicle trans-
por tedawa y. #
Have the components of the high-voltage
on-board electrical system checked at a
qu ali/ed specialist workshop and
re placed if necessar y. The components of
the high-voltage on-board
electrical system are mar ked with yellow warning
stic kers. The cables of the high-voltage on-board
electrical system are orange.
Ve hicles with hybrid systems generate signi/-
cant lyless noise when stationary and when being
driven than vehicles with combustion engines.
When driving in elect ric mode, theve hicle may
not be heard by otherroad users due tothe signif-
icantly reduced noise generated. It is
forth is reason that theve hicle is equipped
with a sound generator, which ser ves as an acous-
tic vehicle alerting system (A VAS). Declar
Declar
ations of conf
ations of conf or
ormity and not
mity and not es on dr
es on driving
iving
in
in di.er
di.er ent
entcountr
countr ies
ies Electr
Electr
omagne
omagne tic com
tic compatibility
patibility The elect
romagnetic compatibility of theve hicle
components has been checked and certi/ed
according tothe cur rently valid version of Regula-
tion UN-R 10. v
v
ehicle inst
ehicle inst alled r
alled radio com
adio com ponents
ponents Onl
Onl
y f
y for EU and EFT
or EU and EFT A countr
A countries and countr
ies and countr ies t
ies that
hat
r
r ecognise t
ecognise t he EU manuf
he EU manuf actur
acturer's declar
er's declar ation of
ation of
conf
conf or
ormity:
mity: The
following information applies toall wireless
components of theve hicle and of the information systems and communication devices integ
rated in
th eve hicle:
The manu facturers of the wireless components
ensure that all wireless components ins talled in
th eve hicle comply with Directi ve2014/53/EU.
The full texts of the EU declarations of conformity
are available at thefo llowing web address:
https://moba.i.daimler.com/mar kets/ece-r ow/
baix/cars/certi/cates-of-con form ity/en_GB/
index.html General no
tes
29
29

th
ese exhaust gases is hazardous tohealth
and leads topoisoning. #
Never lea vetheve hicle or, if present, the
stationa ryheater running in an enclosed
space without su1cient ventilation. &
W
WARNI NG
ARNI NGRisk of /re due to0ammable
material in the engine compartment or the
ex haust system
Flammable materials may ignite. #
Therefore, check regula rly th at there are
no 0ammable materials in the engine
compartment or on theex haust system. R
R
eq
eq uir
uir ements:
ements:
R The key is in theve hicle and is recognised. #
V
Vehicles wit
ehicles wit h manual tr
h manual tr ansmission:
ansmission: Depress
th e clutch pedal. #
V Vehicles wit
ehicles wit h aut
h automatic tr
omatic tr ansmission:
ansmission: ShiT
th e transmission toposition 005Dor005C. #
Depress the brake pedal and press button 1
once. #
Ifth eve hicle does not start: switch o. non-
essential consumers and press but ton1
once. #
Ifth eve hicle still does not start and the dis-
play message Place the key in the marked
space See Owner's Manual appears inthe
inst rument displa y: starttheve hicle with the
ke y in the mar ked space (emer gency ope ra-
tion mode) (/ page 170).
% You can switch o. theve hicle while driving. To
do this, press button 1for about thre e sec-
onds or bypressing button 1thre e times
within thre e seconds. Be sure toobser vethe
saf ety no tes under "Driving tips"
(/ page 173).
Obser veany information rega rding display mes-
sages that can be displ ayed on the inst rument
displa y.
S
S t tar
ar ting t
ting t he v
he vehicle wit
ehicle wit h t
h the ke
he key in t
y in t he mark
he mark ed
ed
space (emerg
space (emerg ency oper
ency oper ation mode)
ation mode)
If th eve hicle does not start and thePlace the
key in the marked space See Owner's Manual
message appears in the inst rument displa y,you can start
theve hicle in emer gency ope ration
mode. Mar
ked space (e xample with cup holder without
co ver) #
Open the co ver of the mar ked space 2if
necessar y. #
Make sure that the mar ked space 2is
em pty. 170 170
Driving and parking

#
Remo vetheke y1 from theke yring. #
Place theke y1 inthe mar ked space 2on
th e symbol 3.
The vehicle will start aTer a short time.
When youre mo vetheke y1 from the mar ked
space 2,theve hicle can be driven. For fur-
th er engine starts ho wever,theke y1 must
be located in the mar ked space 2onthe
symbol 3during the entire journe y. #
Have theke y1 checked at a quali/ed spe-
cialist workshop.
If t
If t he v
he v ehicle does no
ehicle does no t st
t st art:
art: #
Place theke y1 inthe mar ked space 2and
lea veitth ere. #
V
Vehicles wit
ehicles wit h manual tr
h manual tr ansmission:
ansmission: Depress
th e clutch pedal. #
Depress the brake pedal and start theve hicle
using the start/s top button.
% You can switch on the po wer supply or the
ve hicle with the start/s top button. Obser
veany information rega rding display mes-
sages that can be displ ayed on the inst rument
displa y. S
S
t
tar
ar ting t
ting t he v
he vehicle via R
ehicle via R emot
emote Online Ser
e Online Ser vices
vices Cooling or heating t
Cooling or heating t
he v
he vehicle int
ehicle int er
erior bef
ior bef ore
ore
st
st ar
ar ting t
ting t he jour
he jour ney
ney
Ensu rethefo llowing before starting the engine:
R The legal stipulations in the area where your
ve hicle is par ked allow engine starting via
smartphone.
R It is safe tostart and runth e engine where
yo ur vehicle is par ked.
R The fuel tank is su1cient lyfull.
R The star ter battery is su1ciently charge d.
Char
Char ging t
ging t he st
he start
arter batt
er batt er
ery bef
y bef or
ore st
e st ar
arting t
ting t he
he
jour
jour ney
ney
Yo u can receive a message on your smartphone
when the state of charge ofthe star ter battery is
lo w. You can then start theve hicle with the smart-
phone tocharge the batter y.The vehicle is auto-
matically switched o. aTer ten minutes. Ensure
thefo llowing before starting the engine:
R The legal stipulations in the area where your
ve hicle is par ked allow engine starting via
smartphone.
R It is safe tostart and runth e engine where
yo ur vehicle is par ked.
R The fuel tank is su1cient lyfull.
S
S t
tar
ar ting t
ting t he v
he vehicle (R
ehicle (R emot
emot e Online)
e Online) &
W
WARNING
ARNING Risk of crushing or entrapment
due tounintentional starting of the engine
Limbs could be crushed or trapped if the
engine is star ted unintentionally during service
or maintenance work. #
Always secure the engine against unin-
te ntional starting before ca rrying out
main tenance or repair work. R
R
eq
eq uir
uir ements:
ements:
R Park position 005Dis selected.
R The anti-theT alarm system is not activated.
R The hazard warning light system is switched
o.. Driving and parking
171
171

R
Frequent operation in mountainous terrain or
on poor road sur faces
R When the engine is oTen leT idling for long
periods
R Operation in particular lydusty conditions
and/or if air-recirculation mode is frequently
used
In these or similar operating conditions, ha vethe
interior air /lter, air /lter, engine oil and oil /lter,
fo rex ample, changed more frequentl y.The tyres
must be checked more frequently if theve hicle is
operated under increased loads. Further informa-
tion can be obtained at a quali/ed specialist work-
shop. Batt Batt
er
ery disconnection per
y disconnection per iods
iodsThe AS
SYST PLUS service inter val display can cal-
culate the service due date only when the battery
is connected. #
Display and no tedown the service due date
on the inst rument display before disconnect-
ing the battery (/ page 336). Engine com
Engine com
par
partment
tment A
A
ctiv
ctiv e bonne
e bonne t (pedes
t (pedestr trian pr ot
ian pr otection)
ection) Oper
Oper
ation of t
ation of t he activ
he active bonne
e bonne t (pedes
t (pedestr trian pr ot
ian pr otec-
ec-
tion)
tion)
In cer tain accident situations, the actuation of the
active bonnet reduces therisk of injury topedes-
trians. The rear area of the bonnet is raised by
appr oximately 70 mm.
Fo rth e drive tothewo rkshop, reset the actuated
active bonnet yourself (/ page 337).
ATer the active bonnet has been actuated, pedes-
trian pr otection may be limited.
Ha ve the full functionality of the active bonnet
re stored in a quali/ed specialist workshop.
R
R ese ese tting t
tting t he activ
he activ e bonnet
e bonnet &
W
WARNING
ARNING Risk of burns from hot compo-
nent parts in the engine compartment
Cer tain component parts in the engine com-
partment can be very hot, e.g. the engine, the
cooler and parts of theex haust system. #
Allow the engine tocool down and only
to uch component parts described in the
fo llowing. #
With your hand 0at, push down active bonnet
1 inthe area around the hinges on bo th
sides (ar rows ).
In doing so, the actuator is depressurised and
yo u may hear a hissing sound.
The engine bonnet must engage in position. #
Ifth e active bonnet can be raised slightly at
th ere ar in the area of the hinges, repeat the
step until it engages co rrectl y. Maintenance and ca
re
337
337

#
Ifth e bonnet can still be liTed slightl y,open
th e bonnet again and close it with a little force
until it engages cor rectl y. Engine oil
Engine oil
Chec
Chec
king t
king t he engine oil lev
he engine oil lev el using t
el using the on-board
he on-board
com
com put
puter
er
R
R eq
eq uir
uir ements:
ements:
R The engine has been warmed up.
R The vehicle is par ked on a le vel sur face.
R The engine is running at idle speed.
R The bonnet is closed.
The engine oil le vel is de term ined during driving.
De term ining the engine oil le vel can take up to
30 minutes with a normal driving style and even
longer with an active driving style. On-board computer:
4 Service 5
Engine oil level
One of thefo llowing message s will appear onthe
inst rument displa y:
R Engine oil level Measuring now: measu rement
of the oil le vel is not yet possible. #
Repeat there qu est aTer a maximum of
30 minutes' driving.
R Engine oil level OK andthe bar display for
indicating the oil le vel on the inst rument dis-
play is green and is between "min" and "max":
th e oil le vel is cor rect.
R Engine oil level Add 1,0 l andthe bar display
fo r indicating the oil le vel on the inst rument
display is orange and is below "min": #
Add 1 l of engine oil.
R Reduce engine oil level andthe bar display for
indicating the oil le vel on the inst rument dis-
play is orange and is abo ve"max": #
Drain o. any excess engine oil that has been
added. Todo so, consult a quali/ed specialist
wo rkshop.
R For engine oil level turn on ignition #
Switch on theve hicle tocheck the engine oil
le ve l.
R Engine oil level System inoperative: The oil
leve l sensor is defective or not connected. #
Consult a quali/ed specialist workshop.
R Engine oil level System currently unavail. #
Close the bonnet.
T T opping up engine oil
opping up engine oil &
W
WARNING
ARNING Risk of burns from hot compo-
nent parts in the engine compartment
Cer tain component parts in the engine com-
partment can be very hot, e.g. the engine, the
cooler and parts of theex haust system. #
Allow the engine tocool down and only
to uch component parts described in the
fo llowing. 340
340
Maintenance and care

&
W
W ARNI NG
ARNI NGRisk of /re and injury from
engine oil
If engine oil comes into contact with hot com-
ponent parts in the engine compartment, it
may ignite. #
Make sure that no engine oil is spilled
next tothe /ller opening. #
Allow the engine tocool o. and thor-
oughly clean the engine oil from compo-
nent parts before starting theve hicle. *
N
NO OTE
TE Engine damage caused byan inco r-
re ct oil /lter, incor rect oil or additi ves #
Do not use engine oils or oil /lters which
do not cor respond tothe speci/cations
ex plicitly prescribed forth e service inter-
va ls. #
Follow the inst ructions on the service
inter val display forch anging the engine
oil and obser vethe prescribed change
inter vals. #
Do not use additives. *
N
NOOTE
TE Damage caused bytopping up too
much engine oil To
o much engine oil can damage the engine or
th e catalytic con verter. #
Have excess engine oil remo ved at a
qu ali/ed specialist workshop. %
Depending on driving st yle, theve hicle con-
sumes up to0.8 litre of oil per 1000 km. The
oil consum ption may be higher than this when
th eve hicle is new or if you frequently drive at
high engine speeds. #
Turn cap 1anti-clockwise and remo veit. #
Top up the engine oil. #
Replace cap 1and turn it clockwise until it
engages. #
Check the oil le vel again (/ page 340). Maintenance and care
341
341

Chec
Chec
king t
king t he coolant lev
he coolant lev el
el &
W
WARNING
ARNING Risk of burns from hot compo-
nent parts in the engine compartment
Cer tain component parts in the engine com-
partment can be very hot, e.g. the engine, the
cooler and parts of theex haust system. #
Allow the engine tocool down and only
to uch component parts described in the
fo llowing. &
W
WARNING
ARNING Risk of scalding from hot cool-
ant
If yo u open the cap, you could be scalded. #
Let the mo tor cool down before opening
th e cap. #
When opening the cap, wear pr otective
glo ves and saf ety glasses. #
Open the cap slo wlytorelease pressure. #
Park theve hicle on a le vel sur face. #
Check the coolant temp erature display in the
inst rument cluster.
The coolant temp erature must be below 70°C. #
Slowly turn cap 1anti-clockwise torelease
ove rpressure. #
Continue turning cap 1anti-clockwise and
re mo veit. The coolant le
vel is cor rect in thefo llowing cases:
R Ifth e engine is cold, the coolant is up to
mar ker bar 2.
R Ifth e engine is warm,th e coolant is up to
1.5 cm overth e mar ker bar 2. #
If necessar y,top up with coolant that has
been appr ovedfo r Mercedes-Benz.
% Further information on coolant (/ page 404) T
T
opping up t
opping up t he windscr
he windscreen w
een washer syst
asher syst em
em &
W
WARNING
ARNING Risk of burns from hot compo-
nent parts in the engine compartment
Cer tain component parts in the engine com-
partment can be very hot, e.g. the engine, the
cooler and parts of theex haust system. #
Allow the engine tocool down and only
to uch component parts described in the
fo llowing. 342
342
Maintenance and care

#
Tow- start theve hicle while the clutch pedal is
fully depressed. #
Slowly re leasethe clutch pedal. #
Immediately shiT toneutral if the engine
starts. #
Stop theve hicle in accordance with the tra1c
conditions. #
Remo vetheto w bar. #
Remo vetheto wing eye. #
Have theve hicle checked at a quali/ed spe-
cialist workshop. Electr
Electr
ical fuses
ical fuses N
No
ot
tes on electr
es on electr ical fuses
ical fuses &
W
WARNING
ARNING Risk of accident and injury due
to ove rloaded lines
If yo u manipulate or bridge a faulty fuse or if
yo ure place it with a fuse with a higher amper-
age, the electric line could be overloaded.
This could result in a /re. #
Alwaysre place faulty fuses with speci-
/ed new fuses containing the cor rect
amperage. *
N
NOOTE
TE Damage due toincor rect fuses Electrical components or systems may be
damaged
byincor rect fuses, or their function-
ality may be signi/cantly impaired. #
Only use fuses that ha vebeen appr oved
by Mercedes-Benz and which ha vethe
cor rect fuse rating. Blown fuses must be
replaced with fuses of the
same rating, whi chyou can recognise bythe col-
our and the label. The fuse ratings and fur ther
information tobe obser ved can be found in the
fuse assignment dia gram.
F F use assignment diagr
use assignment diagr am:
am:onthe fuse box in the
engine compartment (/ page 372). *
N
NOOTE
TE Damage or malfunctions caused by
moisture Moisture may cause damage
tothe electrical
system or cause it tomalfunction. #
When the fuse box is open, make sure
th at no moisture can enter the fuse box. #
When closing the fuse box, make sure
th at the seal of the lid is positioned cor-
re ctly on the fuse box. If
th e ne wlyinser ted fuse also blo ws, ha vethe
cause traced and recti/ed at a quali/ed specialist
wo rkshop.
Ensure thefo llowing before replacing a fuse:
R The vehicle is secured against rolling away.
R All electrical consume rsare switched o..
R The vehicle is switched o..
The elect rical fuses are located in various fuse
bo xes:
R Fuse box in the engine compartment on the
leT-hand side of theve hicle, when vie wed in
th e direction of tr avel (/ page 372) Breakdown assistance
371
371

R
Fuse box in the front passenger foot we ll
(/ page 372)
R Fuse box in the centre of the load compart-
ment (/ page 373) Opening and closing t
Opening and closing t
he fuse bo
he fuse box in t
x in the engine
he engine
com
com par
partment
tment R
R
eq
eq uir
uir ements:
ements:
R A dry clo thand a scr ewdriver are available.
Obser vethe no tes on elect rical fuses
(/ page 371).
Opening
Opening &
W
WARNING
ARNING Risk of injury from using the
windscreen wipers when the bonnet is
open
If th e windscreen wipers start moving when
th e bonnet is open, you could be trapped by
th e wiper linkage. #
Always switch o. the windscreen wipers
and vehicle before opening the engine
bonnet. #
Open the bonnet. #
Remo veany existing moisture from the fuse
box using a dry clo th. #
Loosen scr ews1. #
Press clamps 2and liT the fuse box lid up
and out. The fuse assignment diag
ram is in a recess on the
side of the fuse box.
Closing Closing #
Check whe ther the seal is positioned cor rectly
in the lid. #
Place the lid on the fuse box. #
Make sure that clamps 2engage. #
Tighten scre ws1. #
Close the bonnet. Opening and closing t Opening and closing t
he fuse bo
he fuse box in t
x in the fr
he front
ont
passeng
passeng er f
er foo
ootw
twell
ell Obser
vethe no tes on elect rical fuses
(/ page 371). 372
372
Breakdown assistance