check engine MERCEDES-BENZ C-CLASS CABRIOLET 2018 Owner's Guide

Warning/
indicator
lampNSignal type
Possible causes/consequences and M
Solutions
?NThe red coolant warning lamp comes on while the engine is running.
The coolant level is too low.
If the coolant level is correct, the airflow to the engine radiator may be blocked or
the electric engine radiator fan may be defective.
The coolant is too hot and the engine is no longer being cooled sufficiently.
XObserve the additional display messages in the multifunction display.
XPull over and stop the vehicle safely and switch off the engine, paying attention
to road and traffic conditions.
XSecure the vehicle against rolling away (Ypage 143).
XLeave the vehicle and keep a safe distance from the vehicle until the engine has cooled down.
XCheck the coolant level and add coolant, observing the warning notes
(Ypage 284).
XIf you have to add coolant frequently, have the engine cooling system checked.
XMake sure that the air supply to the engine radiator is not blocked, e.g. by snow,
slush or ice.
XDo not start the engine again until the coolant temperature gauge is below the
red marking. Otherwise, the engine could be damaged.
XDrive to the nearest qualified specialist workshop.
XAvoid heavy loads on the engine as you do so, e.g. driving in mountainous terrain
and stop-and-go traffic.
?N The red coolant warning lamp comes on while the engine is running. A warning
tone also sounds.
The coolant temperature gauge has reached the red marking. The airflow to the
engine radiator may be blocked or the coolant level may be too low.
GWARNING
The engine is not being cooled sufficiently and may be damaged.
Do not drive when your engine is overheated. This can cause some fluids which
may have leaked into the engine compartment to catch fire.
Steam from the overheated engine can also cause serious burns which can occur
just by opening the hood.
There is a risk of injury.
XObserve the additional display messages in the multifunction display.
XPull over and stop the vehicle safely and switch off the engine, paying attention
to road and traffic conditions.
XSecure the vehicle against rolling away (Ypage 143).
XLeave the vehicle and keep a safe distance from the vehicle until the engine has
cooled down.
XCheck the coolant level and add coolant, observing the warning notes
(Ypage 284).
XIf you have to add coolant frequently, have the engine cooling system checked.
XMake sure that the air supply to the engine radiator is not blocked, e.g. by snow,
slush or ice.
Warning and indicator lamps in the instrument cluster249
On-board computer and displays
Z

Vehicle
Warning/
indicator
lampNSignal type
Possible causes/consequences and M
Solutions
ÐNThe red power steering warning lamp is lit while the engine is running.
The power steering is malfunctioning.
A warning tone also sounds.
GWARNING
You will need to use more force to steer.
There is a risk of an accident.
XCheck whether you are able to apply the extra force required.
If you are able to steer safely:
XDrive on carefully.
XVisit a qualified specialist workshop immediately.
If you are unable to steer safely:
XDo not drive on.
XConsult a qualified specialist workshop.
252Warning and indicator lamps in the instrument cluster
On-board computer and displays

When checking the oil level:
Rpark the vehicle on a level surface
Rthe engine should be switched off for approx-
imately five minutes if the engine is at normal
operating temperature
Rall vehicles (except Mercedes ‑AMG C 63
and Mercedes ‑AMG C 63 S):if the engine is
not at normal operating temperature, e.g. if
the engine was started only briefly, wait
approximately 30 minutes before carrying out
the measurement
Mercedes ‑AMG C 63 and Mercedes ‑AMG C
63 S: the oil level must only be checked when
the engine is at normal operating temperature.
Checking the oil level using the oil dip-
stick
Check the oil level with the oil dipstick (exam-
ple)
XPull oil dipstick :out of the dipstick guide
tube.
XWipe off oil dipstick :.
XSlowly slide dipstick :into the guide tube to
the stop, and take it out again after approx-
imately three seconds.
If the level is between MIN mark =and MAX
mark ;, the oil level is correct.
XIf the oil level has dropped to MIN mark =or
below, add 1.1 US qt (1.0 l)of engine oil.
Adding engine oil
HEnvironmental note
When adding oil, take care not to spill any. If
oil enters the soil or waterways, it is harmful to
the environment.
!Use only engine oils and oil filters that are
approved for vehicles with a service system. A list of the engine oils and oil filters that have
been tested and approved in accordance with
Mercedes-Benz Specifications for Service
Products is available at any authorized
Mercedes-Benz Center.
The following cause engine failure or damage
to the exhaust system:
RUse of engine oils and oil filters that have
not been expressly approved for the service
system
RReplacement of engine oil and oil filter after
the replacement interval specified by the
service system has expired
RUse of engine oil additives
!Do not add too much oil. adding too much
engine oil can result in damage to the engine
or to the catalytic converter. Have excess
engine oil siphoned off.
Add engine oil (example)
XTurn cap :counter-clockwise and remove it.
XAdd engine oil.
If the oil level is at or below the MIN mark on
the oil dipstick, add 1.1 US qt (1.0 l)of engine
oil.
XReplace cap :on the filler neck and tighten
clockwise.
Ensure that the cap locks into place securely.
XCheck the oil level again with the oil dipstick
(Ypage 283).
Further information on engine oil (
Ypage 342).
Engine compartment283
Maintenance and care
Z

Additional service products
Import ant safety notes
GWARNIN G
Certain component sin th eengin ecompart-
ment, suc has th eengine, radiato rand part s
of th eexhaust system, can become ver yhot .
Working in th eengin ecompartmen tposes a
ris kof injury.
Wher epossible, let th eengin ecool down and
touch only th ecomponent sdescribed in th e
following.
GWARNIN G
The engin ecompartmen tcontain smoving
components. Certain components, suc has
th eradiato rfan ,may continu eto run or start
again suddenly when th eignition is off .There
is aris kof injury.
If you need to do any wor kinside th eengin e
compartment:
Rswitch off th eignition
Rnever reac hint oth earea wher ethere is a
ris kof danger from moving components,
suc has th efan rotation area
Rremove jewelr yand watches
Rkeep items of clothing and hair ,for exam-
ple, away from moving part s
GWARNING
The coolin gsystem is pressurized, particularly
when th emotor is warm .If you open th ecap ,
you could be scalded if hot coolan tsprays out .
There is aris kof injury.
Let th eengin ecool down before you open th e
cap .Wear gloves and eye protection .Slowly
open th ecap to reliev epressure.
GWARNIN G
Opening th ehoo dwhen th eengin eis over-
heated or when there is afir ein th eengin e
compartmen tcould expos eyou to hot gase s
or other servic eproducts .There is aris kof
injury.
Let an overheate dengin ecool down before
opening th ehood. If there is afir ein th e
engin ecompartment, keep th ehoo dclosed
and contact th efir edepartment.
Checking coolant level
Checking th ecoolan tlevel (example)
XPark th evehicl eon alevel surface.
Only chec kth ecoolan tlevel when th evehicl e
is on alevel surfac eand th eengin ehas cooled
down .
XTurn th eSmartKey to position 2in th eigni-
tion loc k (Ypage 123).
or
XPress th eStart/Sto pbutto ntwice on vehicles
wit hKEYLESS-GO or th eKEYLESS-GO start
function (
Ypage 124).
XCheckth ecoolan ttemperature display in th e
instrumen tcluste r (Ypage 36).
The coolan ttemperature mus tbe belo w
15 8 ‡ (70 †).
XTurn th eSmartKey to position gin th eigni-
tion loc k (Ypage 123).
or
XPress th eStart/Sto pbutto nonce on vehicles
wit hKEYLESS-GO or th eKEYLESS-GO start
function (
Ypage 124).
XSlowly tur ncap :half atur ncounter-clock -
wise and allow excess pressur eto escape.
XTurn cap :further counter-clockwise and
remove it .
If th ecoolan tis at th elevel of marke rbar =
in th efiller neck when cold, there is enough
coolan tin coolan texpansion tan k;.
If th ecoolan tlevel is approximately 0. 6in
(1. 5cm) abov emarke rbar =in th efiller neck
when warm ,there is enough coolan tin expan -
sion tan k;.
284Engine compartment
Maintenance and care

XPress9or: on the steering wheel to
select the Servicemenu and confirm with
a.
XPress 9or: on the steering wheel to
select the ASSYST PLUSsubmenu and con-
firm with a.
The service due date appears in the multi-
function display.
Information about Service
Resetting the ASSYST PLUS service
interval display
!If the ASSYST PLUS service interval display
has been inadvertently reset, this setting can
be corrected at a qualified specialist work-
shop.
Have service work carried out as described in
the Maintenance Booklet. This may otherwise
lead to increased wear and damage to the
major assemblies or the vehicle.
A qualified specialist workshop, e.g. an author-
ized Mercedes-Benz Center, will reset the
ASSYST PLUS service interval display after the
service work has been carried out. You can also
obtain further information on maintenance
work, for example.
Special service requirements
The specified maintenance interval takes only
the normal operation of the vehicle into
account. Under arduous operating conditions or
increased load on the vehicle, maintenance
work must be carried out more frequently, for
example:
Rregular city driving with frequent intermediate
stops
Rif the vehicle is primarily used to travel short
distances
Ruse in mountainous terrain or on poor road
surfaces
Rif the engine is often left idling for long periods
Under these or similar conditions, have, for
example, the air filter, engine oil and oil filter
replaced or changed more frequently. Under
arduous operating conditions, the tires must be
checked more often. Further information can be obtained at a qualified specialist workshop, e.g.
an authorized Mercedes-Benz Center.
Driving abroad
An extensive Mercedes-Benz Service network is
also available in other countries. You can obtain
further information from any authorized
Mercedes-Benz Center.
Care
General notes
!
For cleaning your vehicle, do not use any of
the following:
Rdry, rough or hard cloths
Rabrasive cleaning agents
Rsolvents
Rcleaning agents containing solvents
Do not scrub.
Do not touch the surfaces or protective films
with hard objects, e.g. a ring or ice scraper.
You could otherwise scratch or damage the
surfaces and protective film.
!Do not park your vehicle for a long period of
time directly after cleaning, particularly after
cleaning the wheel rim with wheel cleaner.
Wheel cleaner can lead to the increased cor-
rosion of the brake discs and pads. Therefore,
drive for a few minutes after cleaning. By
heating up the brakes, the brake discs and
pads dry. The vehicle can then be parked for a
long period of time.
HEnvironmental note
Dispose of empty packaging and cleaning
cloths in an environmentally responsible man-
ner.
Regular care of your vehicle is a condition for
retaining the quality in the long term.
Use care products and cleaning agents recom-
mended and approved by Mercedes-Benz.
Washing the vehicle and cleaning the
paintwork
Automatic car wash
GWARNING
Braking efficiency is reduced after washing
the vehicle. There is a risk of an accident.
286Care
Maintenance and care

XIf possible, bring the front wheels into the
straight-ahead position.
XSwitch off the engine.
XRemove the SmartKey from the ignition lock.
or, in vehicles with KEYLESS-GO start-function
or KEYLESS‑GO
XOpen the driver's door.
The vehicle electronics are now in position
u. which is the same as the SmartKey having
been removed.
XRemove the Start/Stop button from the igni-
tion lock (Ypage 124).
XMake sure that the engine cannot be started
via your smartphone (Ypage 126).
XMake sure that the passengers are not endan-
gered as they do so. Make sure that no one is near the danger area while a wheel is being
changed. Anyone who is not directly assisting
in the wheel change should, for example,
stand behind the barrier.
XGet out of the vehicle. Pay attention to traffic
conditions when doing so.
XClose the driver's door.
Vehicles with MOExtended tires (tires
with run-flat characteristics)
General notes
With MOExtended tires (tires with run flat char-
acteristics), you can continue to drive your vehi-
cle even if there is a total loss of pressure in one
or more tires. The affected tire must not show
any clearly visible damage.
You can recognize a MOExtended tire by the
MOExtended marking which appears on the
sidewall of the tire. You will find this marking
next to the tire size designation, the load-bear-
ing capacity and the speed index (
Ypage 326).
MOExtended tires may only be used in conjunc-
tion with an active tire pressure loss warning
system or with an active tire pressure monitor.
If a pressure loss warning message appears
in the multifunction display:
Robserve the instructions in the display mes-
sages (Ypage 234)
Rcheck the tire for damage
Rif driving on, observe the following notes
The driving distance possible in run-flat mode is
approximately 50 miles (80 km) when the vehi- cle is partially laden. When the vehicle is fully
laden it is approximately 19 miles (30 km).
In addition to the vehicle load, the driving dis-
tance possible depends upon:
Rvehicle speed
Rroad condition
Routside temperature
The driving distance possible in run-flat mode
may be reduced by extreme driving conditions
or maneuvers, or it can be increased through a
moderate style of driving.
The driving distance possible in run-flat mode is
counted from the moment the tire pressure loss
warning appears in the multifunction display.
You must not exceed a maximum permissible
speed of 50 mph (80 km/h).
When replacing one or all tires, please observe
the following specifications for your vehicle's
tires:
Rsize
Rthe type and
Rthe "MOExtended" marking
If a tire has gone flat and cannot be replaced
with a MOExtended tire, a standard tire may be
used as a temporary measure. Make sure that
you use the proper size and type (summer or
winter tires).
Vehicles equipped with MOExtended tires are
not equipped with a TIREFIT kit at the factory. It
is therefore recommended that you additionally
equip your vehicle w
ith a TIREFIT kit if you mount
tires that do not feature run-flat properties, e.g.
winter tires. A TIREFIT kit may be obtained from
a qualified specialist workshop.
Important safety notes
GWARNING
When driving in emergency mode, the driving
characteristics deteriorate, e.g. when corner-
ing, accelerating quickly and when braking.
There is a risk of an accident.
Do not exceed the stated maximum speed.
Avoid abrupt steering and driving maneuvers,
and driving over obstacles (curbs, potholes,
off-road). This applies in particular to a laden
vehicle.
Flat tire297
Breakdown assistance
Z

RIt is particularly important to observe the
described order when connecting and dis-
connecting the jumper cables.
RNever connect or disconnect the battery
terminals while the engine is running.
GWARNING
Battery acid is caustic. There is a risk of injury.
Avoid contact with skin, eyes or clothing. Do
not inhale any battery gases. Do not lean over
the battery. Keep children away from batter-
ies. Wash away battery acid immediately with
plenty of clean water and seek medical atten-
tion.
All vehicles:
HEnvironmental note
Batteries contain dangerous
substances. It is against the
law to dispose of them with
the household rubbish. They
must be collected separately and recycled to protect the
environment.
Dispose of batteries in an
environmentally friendly
manner. Take discharged
batteries to a qualified spe-
cialist workshop or a special
collection point for used bat-
teries.
!Have the battery checked regularly at a
qualified specialist workshop.
Observe the service intervals in the Mainte-
nance Booklet or contact a qualified specialist
workshop for more information.
!Always have work on batteries carried out at
a qualified specialist workshop. Should it, in exceptional circumstances, be
absolutely necessary to disconnect the 12-
volt battery yourself, please observe the fol-
lowing:
RSecure the vehicle to prevent it from rolling
away.
RSwitch off the ignition.
RDisconnect the negative terminal first and
then the positive terminal.
The transmission is locked in position j
after disconnecting the battery.
After the work has been done, install the bat- tery and replace the cover of the positive ter-
minal clamp firmly.
Comply with safety precautions and take pro-
tective measures when handling batteries.
Risk of explosion.
Fire, open flames and smoking are
prohibited when handling the bat-
tery. Avoid creating sparks.
Electrolyte or battery acid is corro-
sive. Avoid contact with skin, eyes or
clothing.
Wear suitable protective clothing,
especially gloves, apron and face-
guard.
Immediately rinse electrolyte or acid
splashes off with clean water. Con-
tact a physician if necessary.
Wear eye protection.
Keep children away.
Observe this Operator's Manual.
For safety reasons, Mercedes-Benz recom-
mends that you only use batteries which have
been tested and approved for your vehicle by
Mercedes-Benz. These batteries provide
increased impact protection to prevent vehicle
occupants from suffering acid burns should the
battery be damaged in the event of an accident.
302Battery (vehicle)
Breakdown assistance

In order for the battery to achieve the maximum
possible service life, it must always be suffi-
ciently charged.
Like other batteries, the vehicle battery may
discharge over time if you do not use the vehicle.
In this case, have the battery disconnected at a
qualified specialist workshop. You can also
charge the battery with a charger recommended
by Mercedes-Benz. Contact a qualified special-
ist workshop for further information.
Have the battery condition of charge checked
more frequently if you use the vehicle mainly for
short trips or if you leave it standing idle for a
lengthy period. Consult a qualified specialist
workshop if you wish to leave your vehicle
parked for a long period of time.
Remove the SmartKey if you park the vehicle
and do not require any electrical consumers.
The vehicle will then use very little energy, thus
conserving battery power.
Charging the 12 V battery
Vehicles with a lithium-ion battery:
!Only use battery chargers with a maximum
charging voltage of 14.4 V.
All vehicles except vehicles with a lithium-
ion battery:
!Only use battery chargers with a maximum
charging voltage of 14.8 V.
GWARNING
During charging and jump-starting, explosive
gases can escape from the battery. There is a risk of an explosion.
Particularly avoid fire, open flames, creating
sparks and smoking. Ensure there is sufficient
ventilation while charging and jump-starting.
Do not lean over a battery.
GWARNING
Battery acid is caustic. There is a risk of injury.
Avoid contact with skin, eyes or clothing. Do
not inhale any battery gases. Do not lean over
the battery. Keep children away from batter-
ies. Wash away battery acid immediately with
plenty of clean water and seek medical atten-
tion.
GWARNING
A discharged battery can freeze at tempera-
tures below freezing point. When jump-start-
ing the vehicle or charging the battery, gases can escape from the battery. There is a risk of
an explosion.
Allow the frozen battery to thaw out before
charging it or jump-starting.
All vehicles:
!Only charge the battery using the jump-
starting connection point.
The jump-starting connection point is in the
engine compartment (
Ypage 304).
XOpen the hood.
XConnect the battery charger to the positive
terminal and ground point in the same order
as when connecting the donor battery in the
jump-starting procedure (
Ypage 304).
Keep away from fire and open flames. Do not
lean over a battery. Never charge the battery if it
is still installed in the vehicle, unless you use a
battery charger which has been tested and
approved by Mercedes-Benz. A battery charger
unit specially adapted for Mercedes-Benz vehi-
cles and tested and approved by Mercedes-
Benz is available as an accessory. It permits the
charging of the battery in its installed position.
Contact an authorized Mercedes-Benz Center
for further information and availability. Read the
battery charger's operating instructions before
charging the battery.
All vehicles except vehicles with a lithium-
ion battery: if the warning and indicator lamps
on the instrument cluster do not light up at low
temperatures, it is very likely that the dis-
charged battery has frozen. In this case you may
neither jump-start the vehicle nor charge the
battery. The service life of a thawed-out battery
may be shorter. The starting characteristics can
be impaired, particularly at low temperatures.
Have the thawed-out battery checked at a quali-
fied specialist workshop.
Vehicles with a lithium-ion battery: at low
temperatures, do not charge a battery which has
been removed using a battery charger. Allow the
battery to warm up gently first, if necessary.
Otherwise, the service life can be shortened and
the starting characteristics impaired, especially
at low temperatures.
Battery (vehicle)303
Breakdown assistance
Z

Jump-starting
For the jump-starting procedure, use only the jump-starting connection point in the engine com-
partment, consisting of a positive terminal and a ground point.
All vehicles except vehicles with a lithium-ion battery:
GWARNING
Battery acid is caustic. There is a risk of injury.
Avoid contact with skin, eyes or clothing. Do not inhale any battery gases. Do not lean over the
battery. Keep children away from batteries. Wash away battery acid immediately with plenty of
clean water and seek medical attention.
GWARNING
During charging and jump-starting, explosive gases can escape from the battery. There is a risk of an explosion.
Particularly avoid fire, open flames, creating sparks and smoking. Ensure there is sufficient ven-
tilation while charging and jump-starting. Do not lean over a battery.
GWARNING
During the charging process, a battery produces hydrogen gas. If a short circuit occurs or sparks
are created, the hydrogen gas can ignite. There is a risk of an explosion.
RMake sure that the positive terminal of a connected battery does not come into contact with
vehicle parts.
RNever place metal objects or tools on a battery.
RIt is important that you observe the described order of the battery terminals when connecting
and disconnecting a battery.
RWhen jump-starting, make sure that the battery poles with identical polarity are connected.
RIt is particularly important to observe the described order when connecting and disconnecting
the jumper cables.
RNever connect or disconnect the battery terminals while the engine is running.
GWARNING
A discharged battery can freeze at temperatures below freezing point. When jump-starting the
vehicle or charging the battery, gases can escape from the battery. There is a risk of an explosion. Allow the frozen battery to thaw out before charging it or jump-starting.
If the warning and indicator lamps do not light up on the instrument cluster when temperatures are low, it is probably because the discharged battery has frozen. In this case, you may neither charge
the battery nor jump-start the vehicle. The service life of a thawed-out battery may be shorter. The
starting characteristics can be impaired, particularly at low temperatures. Have the thawed-out
battery checked at a qualified specialist workshop.
All vehicles:
!Avoid repeated and lengthy starting attempts. Otherwise, the catalytic converter could be
damaged by the non-combusted fuel.
304Jump-starting
Breakdown assistance

XConnect positive terminal:on your veh icleto positive terminal ;of donor battery Cusing the
jumper cable, Always begin with positive terminal :on your own vehicle first.
XStart the engine of the donor veh icleand run itat idling speed.
XConnect negative terminal =of donor battery Cto earth point ?of your vehicle using the
jumper cable. beginning with donor battery Cfirst.
XStart the engine.
XBefore disconnecting the jumper cables, let the engine run for several minutes.
XFirst, remove the jumper cables from ground point? and negative terminal =, then from pos-
itive clamp :and positive terminal ;. Begineach time at the contacts on your own vehicle first.
XClose cover Aof positive terminal :after removing jumper cables.
XFold panel Bshut.
XHave the battery checked at a qualified specialist workshop.
Jump-starting isnot cons idered to bea normal operating condition.
iJumper cables and further information regarding jump-starting can be obtained at any qualified
specialist workshop.
Towing and tow-starting
Important safety notes
GWARNING
Functions relevant to safety are restricted or
no longer availab leif:
Rthe engine isnot running.
Rthe brake system or the power steering is
malfunctioning.
Rthere isa malfunction inthe voltage supply
or the veh icle's electrical system.
If your veh icle is bein g towed, much more
force may benecessary to steer or brake.
There isa risk of an acc ident.
In such cases, use a tow bar. Before to wing,
make sure that the steering moves freely.
GWAR NING
You can no longer steer the veh icle ifthe
steering wheel lock has been engaged. There
is a risk of an acc ident.
Alwa ysswit ch off the ignition when to wingthe
veh icle wit h a tow cable or a tow bar.
GWARNING
When to wingor tow-starting another vehicle
and its weight isgreater than the permissible
gross weight of your vehicle, the:
Rthe to wingeye could detach itself
Rthe vehicle /trailer combination could roll-
over.
There is a risk of an accident.
When towing or tow-starting another vehicle,
its weight should not be greater than the per- missible gross weight of your vehicle.
Details on the permissible gross vehicle weight
of your vehicle can be found on the vehicle iden-
tification plate (
Ypage 339).
!When Active Brake Assist, Distance Pilot
DISTRONIC or the HOLD function is activated,
the vehicle brakes automatically in certain
situations.
To avoid damage to the vehicle, deactivate
these systems in the foll owing or similar sit-
uations:
Rwhen to wingthe vehicle
Rin the car wash
!Make sure that the electric parking brake is
released. Ifthe electric parking brake is faulty,
vis ita qualified specialist workshop.
!Secure the tow rope or tow bar to the to wing
eye only. Otherwise, the vehicle could
become damaged.
306Towing and tow-starting
Breakdown assistance