ECU MERCEDES-BENZ C-CLASS CABRIOLET 2021 Repair Manual

&
WARNING Risk of accident due tolimi‐
te d saf ety-re lated functions during the
to wing process
Saf ety-re lated functions are limited or no lon‐
ge rav ailable in thefo llowing situations:
R the ignition is switched off.
R the brake sy stem or po werst eering sys‐
te m is malfunctioning.
R the energy supply or the on-board electri‐
cal sy stem is malfunctioning.
When your vehicle is then towe daw ay, signif‐
icantly more ef fort may be requ ired tosteer
and brake than is no rmally requ ired. #
Use a tow bar. #
Make sure that thesteering wheel can
mo vefreely before towing theve hicle
aw ay. *
NO
TEDama gedue toexcessive tracti ve
po wer If
yo u pull away sharpl y,the tractive po wer
may be too high and theve hicles could be
damaged. #
Pull away slowly and smoo thly. Loading the
vehicle for transport #
Obser vethe no tes on towing away
( / page 387). #
Connect theto w bar totheto wing eye in
order toload theve hicle.
% You can also attach theto w bar tothe trailer
hitch. #
Vehicles with automatic transmission:
shift the automatic transmission toposition
i.
% Ve
hicles with automatic transmission:
th e automatic transmission may be loc ked in
position jintheeve nt of dama getothe
electrical sy stem. Toshift toi , pr ovide the on-board electrical sy
stem with po wer
( / page 384). #
Load theve hicle onto the transpor ter. #
Vehicles with automatic transmission:
shift the automatic transmission toposition
j. #
Use the electric parking brake tosecure the
ve hicle against rolling away. #
Only secure theve hicle bythe wheels.
Ve hicles with ADS PLUS (Adaptive Damping
Sy stem PLUS) &
WARNING Risk of an accident when
transporting vehicles with Adaptive
Damping Sy stem PLUS
When transporting vehicles with Adaptive
Damping Sy stem PLUS, theve hicle/trailer
combination may begin torock andstart to
skid. #
When transporting, ensure that:
R theve hicle has been loaded onto
th e transpor ter cor rectly Breakdown assis
tance 389

R
theve hicle is secured at all four
wheels with suitable tensioning
st ra ps
R the maximum permissible speed of
60 km/h is not exceeded when
transporting *
NO
TEDama getotheve hicle from secur‐
ing it incor rectly #
After loading, theve hicle must be
secured on all four wheels. Otherwise,
th eve hicle could be damaged. #
A minimum dis tance of 20 cm up wards
and 10cm down wards must be kept to
th e transport platform. #
Secure theve hicle on all four wheels af ter
loading. 4MATIC
vehicles/ vehicles with automatic
transmission #
Make sure that the front and rear axles come
to rest on the same transpor tation vehicle.
* NO
TEDama getothe driv etra in due to
incor rect positioning #
Do not position theve hicle abo vethe
connection point of the transport vehi‐
cle. To
wing eyesto rage location The
towing eye is located in thestow age space
under the boot floor. Installing
theto wing eye #
Press the mark on co ver1 inwa rds and
re mo ve. 390
Breakdown assis tance

#
Only use fuses that ha vebeen appr oved
by Mercedes-Benz and which ha vethe
cor rect fuse rating. Blown fuses mu
stbe replaced with fuses of the
same rating, which you can recognise bythe col‐
our and the label. The fuse ratings and fu rther
information tobe obser ved can be found in the
fuse assignment diagram.
Fu se assignment diag ram: onthe fuse box in
th e boot (/ page 394).
* NO
TEDama geor malfunctions caused
by moisture Moisture may cause dama
getothe electrical
sy stem 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 newly inser ted fuse also blo ws, ha vethe
cause traced and rectified at a qualified special‐
ist workshop.
Ensure thefo llowing before replacing a fuse:
R The vehicle is secured against rolling away.
R All electrical consumers are switched off.
R The ignition is switched off.
The electrical fuses are located in various fuse
bo xes:
R Fuse box in the engine compartment on the
driver's side (/ page 392)
R Fuse box on the driver's side of the cockpit
(/ page 393)
R Fuse box in the front passenger foot we ll
(/ page 394)
R Fuse box in the boot on theright-hand side
of theve hicle, when vie wed in the direction
of tr avel (/ page 394) Opening and closing
the fuse box in the
engine compa rtment Re
quirements:
R A dry clo thand a sc rewdriver are available.
Obse rveth e no tes on electrical fuses
(/ page 391).
Opening &
WARNING Risk of inju ryfrom using the
windscreen wipers while the engine bon‐
net is open
When the engine bonn etis open, and the
windscreen wipers are set in motion, you can
be trapped bythe wiper linkage. #
Alw ays switch off the windscreen wip‐
ers and ignition before opening the
engine bonn et. 392
Breakdown assis tance

shop. The new wheel must ha
vethe
cor rect dimensions. %
The emergency spa rewheel is secured in the
emer gency spa rewheel bag in the boot.
Obser vethefo llowing no tes on fitting an emer‐
ge ncy spa rewheel:
R Check the tyre pressure of the emer gency
spa rewheel fitted. Co rrect the pressure as
necessar y.
R The maximum permissible speed with an
emer gency spa rewheel fitted is 80 km/h.
R Do not fit th e emer gency spa rewheel with
sn ow ch ains.
R Replace the emer gency spa rewheel af ter six
ye ars at the latest, rega rdless of wear.
% Ve
hicles with a tyre pressure loss warn‐
ing sy stem: if an emer gency spa rewheel is
fi tted, the tyre pressure loss warning sy stem
cann otfunction reliabl y.Only restart the sys‐
te m again when the emer gency spa rewheel
has been replaced with a new wheel. Ve
hicles with a tyre pressure monitoring
sy stem: if an emer gency spa rewheel is fit‐
te d, the tyre pressure monitoring sy stem
cann otfunction reliabl y.Fo r a few minutes
af te r an emer gency spa rewheel is fitted, the
sy stem may still display the tyre pressure of
th ere mo ved wheel. Only restart the sy stem
again when the emer gency spa rewheel has
been replaced with a new wheel.
Be sure toalso obse rveth efo llowing fur ther
re lated subjects:
R Notes on tyre pressure (/ page 396)
R Tyre pressure table (/ page 397)
R Notes on fitting tyres (/ page 400) Wheels and tyres
411

Display messages
Possible causes/consequences and M
MSolutions &
WARNING Risk of inju ryor death when using a child restra int sy stem while the front passenger airbag is
enabled
If yo u secure a child in a child restra int sy stem on the front passenger seat and the front passenger airbag is
enabled, the front passenger airbag can deploy in theeve nt of an accident.
The child could be stru ck bythe airbag. #
Ensure, bo thbefore and during the journe y,that thest atus of the front passenger airbag is cor rect.
NEVER use a rear wa rdfacing child restra int on a seat pr otected byan ACTIVE AIRB AGin front of it, DE ATH or
SERIOUS INJU RYtotheCH ILD can occur. #
Stop theve hicle immediately in accordance with the traf fic conditions. #
Makesure that no objects are trapped under the front passenger seat. #
Check thest atus of automatic front passenger airbag actuation (/ page 49).#
If necessar y,consult a qualified specialist workshop immediatel y.
PRE-SAFE inoperative See
Owner's Manual *
The PRE‑SAFE ®
functions are malfunctioning. #
Consult a qualified specialist workshop. Display messages and
warning/indicator lamps 433

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

Display messages
Possible causes/consequences and M
MSolutions #
Initiate a new swivel mo vement (/ page 220). #
When the display message disappears, couple up the trailer and drive on.
If th e display message does not disappear, the trailer hitch is malfunctioning and the ball neck is not loc ked. #
Do not couple up the trailer. Drive on without the trailer. No tethere duced ground clearance due tothe
unlo cked ball nec k. #
Consult a qualified specialist workshop.
*T he trailer hitch will not be operational when theve hicle is stationar y. #
Uncouple the coupled trailer and secure it against rolling away. #
Ifth e ball neck has been folded in: unlockthe ball neck (/ page 220). #
Swivel the ball neck into the end position manually and let it engage. #
Ifth e ball neck has been folded out: unlockthe ball neck (/ page 220). #
Swivel the ball neck beneath the bumper manually and let it engage.
If th e display message does not disappear, the trailer hitch is malfunctioning and the ball neck is not loc ked. #
Do not couple up the trailer. Drive on without the trailer. No tethere duced ground clearance due tothe
unlo cked ball nec k. #
Consult a qualified specialist workshop. 442
Displaymessa ges and warning/indicator lamps

Display messages
Possible causes/consequences and M
MSolutions #
Where necessar y,also secure the par kedve hicle against rolling away.
* The yellow ! indicator lamp and there d! indicator lamp are lit. The elect ric pa rking brake is malfunction‐
ing.
To release: #
Swit chthe ignition off and switch it back on. #
Release the electric parking brake manually (/ page166).
or #
Release the electric parking brake automatically (/ page165).
If it is still not possible torelease the electric parking brake: #
Do not continue driving. Consult a qualified specialist workshop.
* The yellow ! indicator lamp is lit and there d! indicator lamp is flashing. The electric parking brake is mal‐
functioning.
The electric parking brake could not be applied or released. #
Swit chthe ignition off and switch it back on.
To appl y: #
Release and then apply the electric parking brake manually (/ page166).
To release: #
Apply and then release the electric parking brake manuall y.452
Display messages and warning/indicator lamps

Display messages
Possible causes/consequences and M
MSolutions
If it is not possible toapply the electric parking brake or there d! indicator lamp continues toflash: #
Do not continue driving. Consult a qualified specialist workshop. #
Where necessar y,also secure the par kedve hicle against rolling away.
* The yellow ! indicator lamp is lit and there d! indicator lamp flashes for appro ximately ten seconds af ter
th e electric parking brake has been applied or released. It then remains lit or goes out. The electric parking brake is
malfunctioning.
If th est ate of charge istoo lo w: #
Char gethe12 V batter y.
To appl y: #
Switch the ignition off.
The electric parking brake will be applied automaticall y.
If yo u do not wantthe electric parking brake tobe applied, e.g. at an automatic car wash or when theve hicle is
being towe d, lea vethe ignition switched on. This does not include having theve hicle towe d with there ar axle
ra ised.
If th e electric parking brake is not applied automatically: #
Switch the ignition off and switch it back on. #
Release and then apply the electric parking brake manually (/ page166).
If it is still not possible toapply the electric parking brake: Display messages and
warning/indicator lamps 453

Display messages
Possible causes/consequences and M
MSolutions #
Consult a qualified specialist workshop. #
Where necessar y,also secure the par kedve hicle against rolling away.
To release: #
Ifth e conditions for auto matic release are fulfilled and the electric parking brake is not released automaticall y,
re lease the electric parking brake manually (/ page166).
If it is still not possible torelease the electric parking brake: #
Do not continue driving. Consult a qualified specialist workshop.
! Release parking brake *
The red! indicator lamp is flashing.
The electric parking brake is applied while you are driving:
R A condition for auto matic release of the electric parking brake has not been fulfilled (/ page165).
R You are per form ing emer gency braking using the electric parking brake (/ page166). #
Che ckthe conditions for auto matic release of the electric parking brake. #
Release the electric parking brake manually. 454
Display messages and warning/indicator lamps