2018 MERCEDES-BENZ C-CLASS SEDAN ECU

Tires
Display messagesPossible causes/consequences andMSolutions
CheckTirePressureSoonCanada only:
The tire pressure loss warning system has detected a significant loss
in pressure.
A warning tone also sounds.
Possible causes:
Ryou have changed the positions of the wheels and tires or installed
new wheels and tires
Rthe tire pressure in one or more tires has dropped significantly
GWARNING
Tire pressures that are too low pose the following hazards:
Rthey may burst, especially as the load and vehicle speed increase.
Rthey may wear excessively and/or unevenly, which may greatly
impair tire traction.
Rthe driving characteristics, as well as steering and braking, may be
greatly impaired.
There is a risk of an accident.
XStop the vehicle without making any sudden steering or braking
maneuvers. Pay attention to the traffic conditions as you do so.
XSecure the vehicle against rolling away (Ypage 161).
XCheck the tires and, if necessary, follow the instructions for a flat
tire (Ypage 317).
XCheck the tire pressures and, if necessary, correct the tire pressure.
XRestart the tire pressure loss warning system when the tire pres-
sure is correct (Ypage 340).
CheckTirePressureThen Restart RunFlat Indicator
Canada only:
The tire pressure loss warning system generated a display message
and has not been restarted since.
XSet the correct tire pressure in all four tires.
XRestart the tire pressure loss warning system (Ypage 340).
Run Flat IndicatorInoperativeCanada only:
The tire pressure loss warning system is faulty.
XVisit a qualified specialist workshop.
PleaseCorrectTirePressureThe tire pressure is too low in at least one of the tires, or the tire
pressure difference between the wheels is too great.
XCheck the tire pressures at the next opportunity (Ypage 342).
XIf necessary, correct the tire pressure.
XRestart the tire pressure monitor (Ypage 342).
252Displa y messages
On-board computer and displays

Display messagesPossible causes/consequences andMSolutions
Check TiresThe tire pressurein on eor mor etires has dropped significantly. The
whee lposition is displayed in th emultifunction display.
A warning tone also sounds.
GWARNIN G
Tir epressures that are to olow pos eth efollowin ghazards :
Rthey may burst, especially as th eload and vehicl espeed increase.
Rthey may wear excessivel yand/o runevenly, whic hmay greatl y
impair tire traction .
Rthedrivin gcharacteristics ,as well as steering and braking ,may be
greatl yimpaired.
There is aris kof an accident.
XStop th evehicl ewithout making any sudden steering or braking
maneuvers .Pay attention to th etraffic condition sas you do so.
XSecur eth evehicl eagainst rollin gaway (Ypage 161).
XCheckth etires and ,if necessary, follow th einstruction sfor aflat
tire (Ypage 317).
XChec kth etire pressur e (Ypage 342).
XIf necessary, correc tth etire pressure.
Warnin gTir eMal ‐functionThe tire pressur ein on eor mor etires has dropped suddenly. The whee l
position is shown in th emultifunction display.
GWARNIN G
Drivin gwit h a flat tire poses aris kof th efollowin ghazards :
Raflat tire affects th eabilit yto steer or brak eth evehicl e
Ryou could lose control of th evehicl e
Rcontinued drivin gwit h a flat tire will caus eexcessive heat build-up
and possibl y afire
There is aris kof an accident.
XStop th evehicl ewithout making any sudden steering or braking
maneuvers .Pay attention to th etraffic condition sas you do so.
XSecur eth evehicl eagainst rollin gaway (Ypage 161).
XCheckth etires and ,if necessary, follow th einstruction sfor aflat
tire (Ypage 317).
TirePress.Monito rCurrently Unavaila‐ble
Becausethere is interferenc efrom astron gsource of radi owaves, no
signals from th etire pressur esensor sare detected. The tire pressur e
monitor is temporarily malfunctioning .
XDrive on.
The tire pressur emonitor restarts automatically as soo nas th e
problem has been resolved.
TirePress .Sen ‐sor(s) Missin gThere is no signal from th etire pressur esensor of on eor several tires .
The pressur eof th eaffecte dtire is no tdisplayed in th emultifunction
display.
XHav eth efault ytire pressur esensor replace dat aqualified special -
ist workshop .
Display messages253
On-board computer and displays
Z

Display messagesPossible causes/consequences andMSolutions
Driver's DoorOpe n&Transmission Notin PRis kof Vehi‐cle Rollin gAwa y
The driver's door is open or no tfully closed and th etransmission is in
position k,iorh.
A warning tone also sounds.
GWARNIN G
The vehicl emay rol laway.
There is aris kof an accident.
XShift th etransmission to position j.
XSecureth evehicl eagainst rollin gaway (Ypage 161).
XCloseth edriver's door completely.
Onl yShift to 'P'whe nVehicl eisSta‐tionar y
The vehicl eis moving .
XPull overand stop th evehicl esafely as soo nas possible, payin g
attention to roa dand traffic conditions.
XShift th etransmission to position j.
ServiceRequiredDoNot Shift GearsVisit Dealer
You canno tchang eth etransmission position due to amalfunction .
A warning tone also sounds.
If transmission position his selected:
XDrive to aqualified specialist workshop without shifting th etrans -
mission from position h.
If transmission position k,iorj is selected:
XSecur eth evehicl eagainst rollin gaway (Ypage 161).
XNotify aqualified specialist workshop or breakdown service.
ReversingNotPossi‐bleServic eRequiredYou canno tshift int otransmission position kdue to amalfunction .
The transmission position sj, iorh continu eto be available.
A warning tone also sounds.
XVisit aqualified specialist workshop .
Transmission Mal‐function StopAmalfunction has occurred in th emechanical transmission compo -
nents.
A warning tone also sounds. The transmission automatically shift sto
position i.
XPull overand stop th evehicl esafely as soo nas possible, payin g
attention to roa dand traffic conditions.
XShift th etransmission to position j.
XSecureth evehicl eagainst rollin gaway (Ypage 161).
XNotify aqualified specialist workshop or breakdown service.
Display messages25 5
On-board computer and displays
Z

Display messagesPossible causes/consequences andMSolutions
StopVehicl eLeaveEngineRunnin gWaitTransmission Cool‐ing
The transmission has overheated. Pullin gaway can be temporarily
impaire dor no tpossible.
XPull ove rand stop th evehicl esafely as soo nas possible, payin g
attention to roa dand traffic conditions. Do no tcontinu edrivin g
under any circumstances.
XLeav eth eengin erunning.
XWait until th edisplay message disappear sbefore pullin gaway.
NThe trunk lid is open .
XCloseth etrunk lid.
MThe hoo dis open . Awarning tone also sounds.
GWARNIN G
The open hoo dmay bloc kyour vie wwhen th evehicl eis in motion .
There is aris kof an accident.
XPull ove rand stop th evehicl esafely as soo nas possible, payin g
attention to roa dand traffic conditions.
XSecur eth evehicl eagainst rollin gaway (Ypage 161).
XCloseth ehood.
CAt least on edoor is open . Awarning tone also sounds.
XClos eall th edoors.
_
Rea rLef tBackrestNot Latche dorRea rRight Backrest NotLatche d
Vehiclewit hthrough-loading feature in th erear bench seat :
The backrest in th erear is no tengage don th eleft-han dand/o rright -
han dside .
XPush th ebackrest bac kuntil it engages.
_
Rea rCenter Back‐res tNot Engage d
Vehiclewit hthrough-loading feature in th erear bench seat :
The center rear seat backrest is no tengaged.
XPush th ebackrest bac kuntil it engages.
256Display messages
On-board computer and displays

Display messagesPossible causes/consequences andMSolutions
Â
Don't Forget YourKey
The SmartKey is notin th eignition lock. You hav eopened th edriver's
door wit hth eengin eswitched off . Awarning tone sounds
This display message is displayed for amaximum of 60 seconds and is
simply areminder.
XTak eth eSmartKey wit hyou when you leav eth evehicle.
Â
Key Not Detected(whit edisplay message )
The SmartKey is currentl yundetected.
XChange th elocation of th eSmartKey in th evehicle.
If th eSmartKey still canno tbe detected:
XInser tth eSmartKey int oth eignition loc kand tur nit to th edesire d
position .
Â
Key Not Detected(reddisplay message )
The SmartKey is no tin th evehicle.
A warning tone also sounds.
If th eengin eis switched off ,you can no longer loc kth evehicl ecen-
trally or start th eengine.
XPull ove rand stop th evehicl esafely as soo nas possible, payin g
attention to roa dand traffic conditions.
XSecur eth evehicl eagainst rollin gaway (Ypage 161).
XLocate th eSmartKey.
XPress aon thesteering whee lto confirm th edisplay message .
Becausethere is interferenc efrom astron gsource of radi owaves, th e
SmartKey is no tdetecte dwhils tth eengin eis running.
A warning tone also sounds.
XPull ove rand stop th evehicl esafely as soo nas possible, payin g
attention to roa dand traffic conditions.
XSecur eth evehicl eagainst rollin gaway (Ypage 161).
XInsertth eSmartKey int oth eignition loc kand drive in SmartKey
mode.
Â
Remove 'Start 'But ‐ton and Insert Key
The SmartKey is continually undetected.
The SmartKey detection function has atemporar ymalfunction or is
faulty. Awarning tone also sounds.
XInser tth eSmartKey int oth eignition loc kand tur nit to th edesire d
position .
XVisitaqualified specialist workshop .
Warning and indicat orlamps in the instrume nt cluster
General notes
Some systems carry out aself-diagnosis when th eignition is switched on .Therefore ,som eindicator
and warning lamp smay ligh tup or flas htemporarily. This behavio ris non-critical .These indicator
and warning lamp sonly indicat e amalfunction if they ligh tup or flas hafter starting th eengin eor
whils tdriving.
258Warning and indicator lamps in the instrument cluster
On-board computer and displays

Safety
Seat belts
Warning/
indicator
lampNSignal type
Possible causes/consequences and M
Solutions
üNAfter starting the engine, the red seat belt warning lamp lights up for six sec-
onds.
The seat belt warning lamp reminds the driver and front passenger to fasten their
seat belts.
XFasten your seat belt (Ypage 48).
üN After starting the engine, the red seat belt warning lamp lights up. In addition, a
warning tone sounds for up to six seconds.
The driver's seat belt is not fastened.
XFasten your seat belt (Ypage 48).
The warning tone ceases.
üN The red seat belt warning lamp lights up after the engine starts, as soon as the
driver's or the front-passenger door is closed.
The driver or front passenger has not fastened their seat belt.
XFasten your seat belt (Ypage 48).
The warning lamp goes out.
There are objects on the front-passenger seat.
XRemove the objects from the front-passenger seat and stow them in a secure
place.
The warning lamp goes out.
üN The red seat belt warning lamp flashes and an intermittent audible warning
sounds.
The driver or front passenger has not fastened their seat belt. The vehicle is being
driven faster than 15 mph (25 km/h) or has briefly been driven faster than 15 mph
(25 km/h).
XFasten your seat belt (Ypage 48).
The warning lamp goes out and the intermittent warning tone ceases.
There are objects on the front-passenger seat. The vehicle is being driven faster
than 15 mph (25 km/h) or has briefly been driven faster than 15 mph (25 km/h).
XRemove the objects from the front-passenger seat and stow them in a secure
place.
The warning lamp goes out and the intermittent warning tone ceases.
Warning and indicator lamps in the instrument cluster259
On-board computer and displays
Z

Safety systems
Warning/
indicator
lampNSignal type
Possible causes/consequences and M
Solutions
$JN$ (USA only), J(Canada only): the red brake system warning lamp is lit
while the engine is running.
A warning tone also sounds.
GWARNING
The brake boosting effect is malfunctioning and the braking characteristics may be
affected.
There is a risk of an accident.
XPull over and stop the vehicle safely as soon as possible, paying attention to road
and traffic conditions. Do not continue driving under any circumstances.
XSecure the vehicle against rolling away (Ypage 161).
XConsult a qualified specialist workshop.
XObserve the additional display messages in the multifunction display.
$JN $ (USA only), J(Canada only): the red brake system warning lamp lights
up while the engine is running.
A warning tone also sounds.
There is not enough brake fluid in the brake fluid reservoir.
GWARNING
The braking effect may be impaired.
There is a risk of an accident.
XPull over and stop the vehicle safely as soon as possible, paying attention to road
and traffic conditions. Do not continue driving under any circumstances.
XSecure the vehicle against rolling away (Ypage 161).
XDo not add brake fluid. Adding more will not correct the malfunction.
XConsult a qualified specialist workshop.
XObserve the additional display messages in the multifunction display.
$N USA only: the red brake system warning lamp is lit while the engine is running.
The multifunction display also shows a display message with the #symbol.
The brake pads/linings have reached their wear limit.
XVisit a qualified specialist workshop.
260Warning and indicator lamps in the instrument cluster
On-board computer and displays

Engine
Warning/
indicator
lampNSignal type
Possible causes/consequences and M
Solutions
;NThe yellow Check Engine warning lamp lights up while the engine is running.
There may be a malfunction, for example:
Rin the engine management
Rin the fuel injection system
Rin the exhaust system
Rin the ignition system (for vehicles with gasoline engines)
Rin the fuel system
The emission limit values may be exceeded and the engine may be in emergency
mode.
XVisit a qualified specialist workshop immediately.
In some states, you must immediately visit a qualified specialist workshop as soon as the yellow Check Engine warning lamp lights up. This is due to the legal require-
ments in effect in these states. If in doubt, check whether such legal regulations
apply in the state in which you are currently driving.
Vehicles with a diesel engine: the fuel tank has been run dry (
Ypage 158).
XStart the engine three to four times after refueling.
If the yellow Check Engine warning lamp goes out, emergency running mode is
canceled. The vehicle need not be checked.
8N The yellow reserve fuel warning lamp lights up while the engine is running.
The fuel level has dropped into the reserve range.
XRefuel at the nearest gas station.
8N The yellow reserve fuel warning lamp flashes while the vehicle is in motion.
In addition, the ;Check Engine warning lamp may light up.
The fuel filler cap is not closed correctly or the fuel system is leaking.
XCheck that the fuel filler cap is correctly closed.
XIf the fuel filler cap is not correctly closed: close the fuel filler cap.
XIf the fuel filler cap is closed:visit a qualified specialist workshop.
?NThe red coolant warning lamp lights up while the engine is running and the
coolant temperature gauge is at the start of the scale.
The temperature sensor for the coolant temperature gauge is malfunctioning.
The coolant temperature is no longer being monitored. There is a risk of engine
damage if the coolant temperature is too high.
XPull over and stop the vehicle safely and switch off the engine, paying attention
to road and traffic conditions. Do not continue driving under any circumstances.
XSecure the vehicle against rolling away (Ypage 161).
XConsult a qualified specialist workshop.
Warning and indicator lamps in the instrument cluster265
On-board computer and displays
Z