check engine MERCEDES-BENZ C-CLASS CABRIOLET 2021 User Guide

R
NOx exhaust gas af tertre atment malfunc‐
tions #
Avoid impurities in AdBlue ®
. Ad
Blue ®
re sidues cr ystallise af ter a period of
time, and contamina tethe sur faces wi thwhich
th ey come into contact. Clean the dirty sur faces
wi th wate r as soon as possible.
When you open theAd Blue ®
tan k,small
amounts of ammonia vapour may escape. Do
not inhale any ammonia vapours that may be
re leased. Only fill th eAd Blue ®
tank in well-venti‐
lated areas.
Ad Blue ®
filling capacity and consum ption Model
Total capacity
All models 14litres Ad
Blue ®
consu mption
The average AdBlue ®
consu mption is between
1% and 5% of fuel consumption. Li kefuel con‐
sum ption, AdBlue ®
consu mption is highly dependent upon driving
style and operating con‐
ditions. Forth is reason, your vehicle's actual
consum ption figures under da y-to -day operating
conditions may di ffer from the consum ption fig‐
ures calculated. The frequency at which you will
ha ve to to p up AdBlue ®
will also vary. Ha vethe
Ad Blue ®
supply checked at a qualified specialist
wo rkshop before making journe ysoutside of
Europe. Before a longer stay outside of Europe,
consult a qualified specialist workshop.
Ad Blue ®
ra nge and fill le vel
The AdBlue ®
fill le vel and range can be displ ayed
via the on-board computer. The AdBlue ®
ra nge
shown depends strongly on the driving style and
operating conditions. The actual range can
th erefore deviate from thera nge cur rently dis‐
pl ay ed in the on-board computer. The informa‐
tion supplied in the Owner's Manual rega rding
th ere ser vequantity at thefirs t display warning
and on the minimum top-up quantity when the
ta nk is em pty is also tobe under stood as guide
va lues. Engine oil
Note
s on engine oil
Obser vethe no tes on operating fluids
(/ page 416). *
NO
TEEngine dama gecaused byan
incor rect oil filter, incor rect oil or addi‐
tives #
Do not use engine oils or oil filters
which do not cor respond tothe specifi‐
cations explicitly prescribed forthe
service inter vals. 422
Tech nical da ta

Display messages
Possible causes/consequences and M
MSolutions
Hazard warning lamps mal-
functioning *T
he hazard warning lamp switch is malfunctioning. #
Consult a qualified specialist workshop. Ve
hicle Display messages
Possible causes/consequences and M MSolutions
d Vehicle is operational
Switch off ignition before
exiting *Y
ou are leaving theve hicle in a ready-to-drive state. #
When you lea vetheve hicle, switch off the ignition, secure theve hicle against rolling away and take theke y with
yo u. #
Ifyo u do not lea vetheve hicle, switch off the electrical consumers, e.g. the seat heating. Otherwise, the12 ‑V
battery may discharge and starting the engine may be possible only with the help of a second battery (jump
st art).
ï
Check trailer hitch lock *T
he trailer hitch is not operational during a journey with a trailer. &
WARNING Risk of an accident if the ball neck is not loc ked
The trailer may become de tach ed. #
Stop theve hicle immediately in accordance with the traf fic conditions. Do not continue driving. #
Uncouple the trailer and secure it against rolling away. #
Initiate a new swivel mo vement and do not re-couple the trailer until thewa rning/indicator lamp goes out. Display messages and
warning/indicator lamps 441

Engine
Display messages
Possible causes/consequences and M
MSolutions
To switch off the engine,
press Start/Stop button
for at least 3 seconds or 3
times. *Y
ou ha vepressed thest art/ stop button while theve hicle is in motion. #
Information about switching off the engine while driving (/ page138).
+ Top up coolant See Own-
er’s Manual *T
he coolant le vel is too lo w.
* NO
TEEngine dama gedue toinsuf ficient coolant #
Avoid long journe yswith insuf ficient coolant. #
Add coolant (/ page 361). #
Have the engine cooling sy stem checked at a qualified specialist workshop.
ÿ
Coolant Stop vehicle
Switch engine off *T
he coolant is too hot. #
Stop theve hicle immediately in accordance with the traf fic conditions and switch off the engine. 446
Displaymessa ges and warning/indicator lamps

Display messages
Possible causes/consequences and M
MSolutions
T
!
÷ inoperative See Owner's
Manual *
EBD, ABS and ESP ®
are malfunctioning.
Other driving sy stems and driving saf ety sy stems (e.g. BAS) may also be malfunctioning. &
WARNING Risk of skidding if EBD, ABS and ESP ®
are malfunctioning
The wheels may block du ring braking and ESP ®
does not pe rform any vehicle stabilization.
The steerability and braking characteristics are heavily impaired and the braking dis tance may increase. In addi‐
tion, other driving saf ety sy stems are switched off. #
Drive on carefull y. #
Have the brake sy stem checked immediately at a qualified specialist workshop. Active Brake Assist Func-
tions currently limited See
Owner's Manual *
Ve hicles with the Driving Assistance Package: Active Brake Assi stwith cross-traf fic function, Evasi veSteering
Assist or PRE‑SAFE ®
PLUS are temp orarily una vailable or only partially available.
Ve hicles without the Driving Assistance Package: Active Brake Assi stistemp orarily una vailable. #
Drive on.
As soon as the ambient conditions are within the sy stem limits, the sy stem will become available again. #
Ifth e display message does not disappear, stop theve hicle in accordance with the tra ffic conditions and restart
th e engine. 47 0
Displaymessa ges and warning/indicator lamps

Engine oil
Display messages
Possible causes/consequences and M
MSolutions
5 Check engine oil level
when next refuelling *T
he engine oil le vel has dropped tothe minimum le vel.
* NO
TEEngine dama gecaused bydriving with insuf ficient engine oil #
Avoid long journe yswith insuf ficient engine oil. #
Check the engine oil le vel when next refuelling.
To p up the engine oil (/ page 359).
No tes on engine oil (/ page 422).
5
Add 1 litre engine oil when
next refuelling *D
isplay message only for cer tain engines:
The engine oil le vel has dropped tothe minimum le vel.
* NO
TEEngine dama gecaused bydriving with insuf ficient engine oil #
Avoid long journe yswith insuf ficient engine oil. #
When next refuelling, add 1 litre of engine oil (/ page 359).
No tes on engine oil (/ page 422). Display messages and
warning/indicator lamps 483

Display messages
Possible causes/consequences and M
MSolutions
5 Engine oil level Reduce oil
level *D
isplay message only for cer tain engines:
The engine oil le vel is too high.
* NO
TEEngine dama gecaused bydriving with excess engine oil #
Avoid long journe yswith excess engine oil. #
Consult a qualified specialist workshop immediately and ha vethe engine oil le velre duced.
5 Engine oil level Stop vehi-
cle Switch engine off *D
isplay message only for cer tain engines:
The engine oil le vel is too lo w.
* NO
TEEngine dama gecaused bydriving with insuf ficient engine oil #
Avoid long journe yswith insuf ficient engine oil. #
Stop theve hicle immediately in accordance with the traf fic conditions. Do not continue driving. #
Switch off the engine. #
Add 1 l of engine oil (/ page 359). #
Check the engine oil le vel.
No tes on engine oil (/ page 422).484
Display messages and warning/indicator lamps

Occupant saf
ety Wa
rning/indicator lamp
Possible causes/consequences and M
MSolutions
6 Re stra int sy stem warning
lamp *T
he redre stra int sy stem warning lamp is lit while the engine is running.
The restra int sy stem is malfunctioning (/ page 38). &
WARNING Risk of inju rydue tomalfunctions in there stra int sy stem
Components in there stra int sy stem may be activated unintentionally or not deploy as intended in an accident. #
Have there stra int sy stem checked and repaired immediately at a qualified specialist workshop. #
Drive on carefully. #
Notethe messages on the multifunction displa y. #
Consult a qualified specialist workshop immediatel y.
ü
Seat belt warning lamp *T
he red seat belt warning lamp flashes and an intermit tent wa rning tone sounds.
or
The red seat belt warning lamp lights up once the engine has star ted.
In addition, an intermittent warning tone may sound.
The red seat belt warning lamp flashes and an intermit tent wa rning tone sounds:
The driver or front passenger has not fastened his or her seat belt while theve hicle is in motion. #
Fasten your seat belt (/ page 42).
There are objects on the front passenger seat. Display messages and
warning/indicator lamps 487

Wa
rning/indicator lamp
Possible causes/consequences and M
MSolutions
R The coolant pump is faulty
If th ere is an additional warning tone, the coolant temp erature has exceeded 120°C. &
WARNING Risk of bu rns when opening the bonn et
If yo u open the bonn etwhen the engine has overheated or when there is a fire inthe engine compartment, the
fo llowing situations may occur:
R You could come into contact with hot gases.
R You could come into contact with other hot, escaping operating fluids. #
Before opening the bonn et, allow the engine tocool down. #
Intheeve nt of a fire inthe engine compartment, keep the bonn etclosed and call thefire service. #
Stop theve hicle immediately in accordance with the traf fic conditions and switch off the engine. Do not continue
driving. #
Notethe messages on the multifunction displa y.
If th e coolant temp erature display is at the lo wer end of thete mp erature scale: #
Consult a qualified specialist workshop.
If th e coolant temp erature display is at the upper end of thete mp erature scale: #
Exit theve hicle and keep a safe dis tance from it until the engine has cooled down. #
Check the coolant le vel (/ page 361). 490
Display messages and warning/indicator lamps

Wa
rning/indicator lamp
Possible causes/consequences and M
MSolutions #
Make sure that the air supply tothera diator is not obstructed. #
Avoiding high loads on the engine, drive tothe nearest qualified specialist workshop. In doing so, ensure that the
coolant temp erature display remains below 120°C.
; Engine diagnosis warning
lamp *T
he yellow engine diagno stics warning lamp is lit while the engine is running.
A malfunction has occu rred in the engine, theex haust sy stem or the fuel sy stem.
The emissions limit value may ha vebeen exceeded and the engine may be running in eme rgency operation mode. #
Have theve hicle checked as soon as possible at a qualified specialist workshop.
Ve hicles with a diesel engine: the fuel tank may ha vebeen run dr y. #
Start the engine thre eto four times af terre fuelling.
If th eye llow engine diagnosis warning lamp goes out, emer gency operation mode is cancelled. The vehicle need
not be checked.
#
Elect rical fault warning
lamp *T
hered elect rical fault warning lamp is lit.
There is a fault in the electrics. #
Notethe messages on the multifunction displa y. Displ
aymessa ges and warning/indicator lamps 491

Wa
rning/indicator lamp
Possible causes/consequences and M
MSolutions
J Brake sy stem warning lamp
(yellow) *T
he yellow brake sy stem warning lamp is lit while the engine is running. &
WARNING Risk of an accident due toa brake sy stem malfunction
If th e brake sy stem is malfunctioning, braking characteristics may be impaired. #
Drive on carefull y. #
Have the brake sy stem checked immediately at a qualified specialist workshop. #
Adjust your speed and drive on carefull y,leaving a suitable dis tance totheve hicle in front. #
Ifth e multifunction display sho wsa display message, obse rve it. #
Consult a qualified specialist workshop.
J Brake sy stem warning lamp
(red) *T
he red brake sy stem warning lamp is lit while the engine is running.
Po ssible causes:
R The brake forc e boosting is malfunctioning and the braking characteristics may be af fected.
R The reis insuf ficient brake fluid in the brake fluid reser voir. #
Notethe messages on the multifunction displa y. &
WARNING Risk of accident and inju ryif brake forc e boosting is malfunctioning
If brake forc e boosting is malfunctioning, increased brake pedal forc e may be necessary for braking. The braking
ch aracteristics may be impaired. The braking dis tance can increase in emergency braking situations. Display messa
ges and warning/indicator lamps 493