ECU MERCEDES-BENZ G-CLASS 2018 Service Manual

Display messagesPossible causes/consequences andMSolutions
TCShiftConditionsNot Fulfilled
Select NEUTRA LGea r
You hav eno tmet on eor mor eshift conditions.
XShift th eautomatic transmission int oneutral position i.
XRepeat thegearshift process.
TCShiftCondition sNot Fulfilled
Max.Speed 40 mph
You hav eexceeded th emaximum speed for th egearshift process.
XDrive mor eslowly.
XRepeat th egearshift process.
LOW RANGE
On
The transfer cas eis in th eLOW RANGE off-road gear.
HIGHRANGE
On
The transfer cas eis in th eHIG HRANGE on-road position .
Differential LocksAvailable OnlyInLOW RANGE
The LOW RANGE butto nhas been pressed. The transfer cas eis in
LOW RANGE off-road gear and adifferential loc kis engaged.
XDisengage th edifferential loc k (Ypage 151).
XRepeat thegearshift process.
TC NEUTRA L
On
The transfer cas eis in th eNeutral neutral position .
A warning tone will also soun dwhen th edriver's door is opened and
th ebrak epedal is no tdepressed.
XClos eth edriver's door .
XSecureth evehicl eagainst rollin gaway (Ypage 122).
XShift th etransfer cas eaccording to drivin gcondition s
(Ypage 149).
Differential Loc kPreselected
ESP Not Available
Adifferential loc kwas engaged. The differential gear system has no t
yet locke dth erespective differential. The activation indicator lamp
(yellow) (
Ypage 151) of th eswitch lights up.
ES P®is unavailable .
AB Sis still available.
Differential LocksActive
ABS and ESP NotAvailable
A differential loc kwas engage dand th edifferential gear system has
locke dth erespective differential. The yellow activation indicator lamp
and red function indicator lamp (
Ypage 151) on theswitch lights up.
AB Sand ES P®are unavailable .
184Display messages
On-board computer and displays

Tires
Display messagesPossible causes/consequences andMSolutions
Tire pressure willbe displayed afterdriving a fewminutes
The tire pressure monitor is measuring the tire pressure.
XDrive on.
The tire pressures appear in the multifunction display after you have
been driving for a few minutes.
TirePress.MonitorInoperativeThe tire pressure monitor is faulty.
XVisit a qualified specialist workshop.
Tire Pressure Moni‐tor Inoperative NoWheel Sensors
The wheels mounted do not have a suitable tire pressure sensor. The
tire pressure monitor is deactivated.
XMount wheels with suitable tire pressure sensors.
The tire pressure monitor is activated automatically after driving for
a few minutes.
Check TiresThe tire pressure in one or more tires has dropped significantly. The
wheel position is shown in the multifunction display.
A warning tone also sounds.
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 122).
XIf there is a flat tire, inspect the tires (Ypage 246).
XCheck the tire pressure (Ypage 263).
XIf necessary, correct the tire pressure.
Displa y messages187
On-board computer and displays
Z

Display messagesPossible causes/consequences andMSolutions
WarningTir eMal ‐functionThe tire pressur ein on eor mor etires has dropped suddenly. The whee l
position is shown in th emultifunction display.
A warning tone also sounds.
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 122).
XIf there is aflat tire, inspec tth etires (Ypage 246).
PleaseCorrec tTirePressureThe tire pressur eis to olow in at least on eof th etires ,or th etire
pressur edifference between th ewheels is to ogreat.
XChec kth etire pressures at th enext opportunity (Ypage 263).
XIf necessary, correc tth etire pressure.
XRestart th etire pressur emonitor (Ypage 265).
TirePress .Sen ‐sor(s) Missin gThere is no signal from th etire pressur esensor of on eor several
wheels. The pressur eof th eaffecte dtire does no tappear in th emul-
tifunction display.
XHav eth efault ytire pressur esensor replace dat aqualified special -
ist workshop .
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.
188Display messages
On-board computer and displays

Display messagesPossible causes/consequences andMSolutions
h
TirePressure Warn‐ing ,Tir eMalfunc‐tio n
The tire pressur ein on eor mor etires has dropped suddenly. The whee l
position is shown on th emultifunction display.
A warning tone also sounds.
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 122).
XIf there is aflat tire, inspec tth etires (Ypage 246).
h
Check Tir ePressure
The tire pressur ein on eor mor etires has dropped significantly. The
whee lposition is shown on 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 yimpaire d
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 122).
XIf there is aflat tire, inspec tth etires (Ypage 246).
XChec kth etire pressur e (Ypage 263).
XIf necessary, correc tth etire pressure.
h
PleaseCorrec tTirePressure
The tire pressur eis to olow in at least on eof th etires ,or th etire
pressur edifference between th ewheels is to ogreat.
XChec kth etire pressures at th enext opportunity (Ypage 263).
XIf necessary, correc tth etire pressure.
Display messages18 9
On-board computer and displays
Z

Vehicle
Display messagesPossible causes/consequences andMSolutions
Shiftto'P'or'N'to Start EngineYou have attempted to start the engine with the transmission in posi-
tionkorh.
XShift the transmission to position jori.
Auxiliary BatteryMalfunctionThe auxiliary battery for the automatic transmission is no longer being
charged.
XVisit a qualified specialist workshop at the next opportunity.
XUntil then, set the automatic transmission to jbefore you switch
off the engine.
XBefore leaving the vehicle, apply the parking brake.
Apply Brake toShift from 'P'You attempted to shift the transmission to position h,kori
without depressing the brake pedal.
XDepress the brake pedal.
Apply Brake toSelect RYou have attempted to shift from position hto position kwithout
applying the brakes.
XDepress the brake pedal.
XShift the transmission to position k.
AThe rear door is open.
GWARNING
When the engine is running, exhaust gases can enter the vehicle inte-
rior if the rear door is open.
There is a risk of poisoning.
XClose the rear door.
?The hood is open.
A warning tone also sounds.
GWARNING
The open hood may block your view when the vehicle is in motion.
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.
XSecure the vehicle against rolling away (Ypage 122).
XClose the hood.
CAt least one door is open.
A warning tone also sounds.
XClose all the doors.
190Display messages
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 6 seconds.
The seat belt warning lamp reminds the driver and front passenger to fasten their
seat belts.
XFasten your seat belt (Ypage 41).
üN After starting the engine, the red seat belt warning lamp lights up. In addition, a
warning tone sounds for up to 6 seconds.
The driver's seat belt is not fastened.
XFasten your seat belt (Ypage 41).
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 41).
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 41).
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.
192Warning and indicator lamps in the instrument cluster
On-board computer and displays

Safety systems
Warning/
indicator
lampNSignal type
Possible causes/consequences and M
Solutions
JNCanada only: the red brake system warning lamp is on while the engine is
running.
A warning tone also sounds.
GWARNING
The brake system is malfunctioning and the braking characteristics may be affec-
ted.
There is a risk of an accident.
XIf the multifunction display shows a display message, please observe this.
XDrive on carefully.
XVisit a qualified specialist workshop.
$JN $ (USA only): the red brake system warning lamp is on while the engine is
running.
J (Canada only): the yellow 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 122).
XConsult a qualified specialist workshop.
XObserve the additional display messages in the multifunction display.
$JN $ (USA only): the red brake system warning lamp is on while the engine is
running.
J (Canada only): the yellow brake system warning lamp is lit 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 122).
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.
Warning and indicator lamps in the instrument cluster193
On-board computer and displays
Z

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
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.
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 122).
XConsult a qualified specialist workshop.
Warning and indicator lamps in the instrument cluster199
On-board computer and displays
Z

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 122).
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 234).
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 H
marking (Ypage 161). 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.
The coolant temperature gauge has exceeded the Hmarking (
Ypage 161). 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 122).
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 234).
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.
200Warning and indicator lamps in the instrument cluster
On-board computer and displays

Tires
Warning/
indicator
lampNSignal type
Possible causes/consequences and M
Solutions
hNThe yellow tire pressure monitor warning lamp (pressure loss/malfunction) is lit.
The tire pressure monitor has detected a loss of pressure in at least one of the tires.
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 trac-
tion.
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 122).
XObserve the additional display messages in the multifunction display.
XCheck the tires and, if necessary, follow the instructions for a flat tire
(Ypage 246).
XCheck the tire pressure (Ypage 263).
XIf necessary, correct the tire pressure.
hN The yellow tire pressure monitor warning lamp (pressure loss/malfunction)
flashes for approximately one minute and then remains lit.
The tire pressure monitor is faulty.
GWARNING
The system is possibly unable to recognize or register low tire pressure.
There is a risk of an accident.
XObserve the additional display messages in the multifunction display.
XVisit a qualified specialist workshop immediately.
202Warning and indicator lamps in the instrument cluster
On-board computer and displays