Check engine MERCEDES-BENZ M-Class 2012 W166 Owner's Guide

Engine
Displ
aymes sage s Possib
lecau ses/cons equences andM Solu
tions +
Che
ckCoolant Lev
elSee Ope
rator'sMan ual The
coolant levelis toolow.
X Add coolant ,obse rving thewarn ingnoteswhen doingso
(Y page 315).
X Ifcoo lant needs tobe added moreoft en than usual, havethe
en gin ecoo lant systemcheck edataqualifie dspec ialist
work shop. G
WAR
NING Do
notspill antif reeze onhot engin eparts. Antifr eeze contains ethylene glycolwhich mayburn
if it comes intocon tact with hotengin eparts. Youcould beseriously burned.
! The coolant levelistoo low. Avoid makin glong journ eyswith toolittlecoolant inthe cooling
system. Theengin ewill other wisebedamaged.
The display messages andthecorr espondin gsymbol thatindicat ethat thecoolant levelis
too low must notbeignored. 254
Display
messagesOn-board computer and displays

Disp
laymessa ges Poss
iblecauses/c onseq uences and M Solu
tions ?
Coo
lantLev elLow Sto
pVeh icl eTur n Eng
ine Off The
coolan tistoo hot.
X Pull over andstop thevehicle safelyandswitch offthe engine,
pay ing attent iontoroad andtraffic conditions.
X Make surethattheairsuppl yto the engine radiatorisnot
blocked, e.g.bysnow, slushorice.
X Wait untilthedispla ymessage disappearsbefore restarting the
engine. Otherwise, thereisarisk ofengine damage .
X Pay attent iontothe coolant temperature display.
X Ifthe temperature increasesagain,visit aqual ified speciali st
workshop immediately . The
poly-V-belt mayhave torn.
X Pull over andstop thevehicle safelyandswitch offthe engine,
pay ing attent iontoroad andtraffic conditions.
X Open thehood.
X Check whether thepoly-V-belt istorn.
If the poly-V-belt istorn:
! Donot cont inue driving. Theengine couldotherwise overheat.
X Consult aqual ified speciali stworkshop.
If the poly-V-belt isnot dam aged:
X Wait untilthedispla ymessage disappearsbefore restarting the
engine. Otherwise, thereisarisk ofengine damage .
X Pay attent iontothe coolant temperature display.
X Visit aqual ified speciali stworkshop. G
WARNING Driving
whenyourengine isoverheated cancause somefluidswhich mayhave leaked intothe
engine compartment tocatch fire.Youcould beseriously burned.
Steam fromanoverheated enginecancause serious burnswhich canoccur justbyopening the
engine hood.Stayawayfrom theengine ifyou seeorhear steam coming fromit.
Stop thevehicle inasafe location awayfrom other traffic. Turnoffthe engine, getout ofthe
vehicle anddonot stand nearthevehicle untiltheengine hascooled down.
! Ifthe coolant temperature exceeds248‡(120 †)donot cont inue driving. Theengine will
otherwise bedamage d. Dis
play messages
255On-board computer and displays Z

Disp
laymessa ges Poss
iblecauses/c onseq uences and M Solu
tions ? The
engin efan isdef ective.
X At coolan ttemperatures under248‡(120 †),drive tothe next
qualified specialist workshop.
X Avo idsubjec tingthe engin etoheavy loads, e.g.driving in
mountainous terrain,andstop- and-go traffic. # The
battery isnot being charged.
Possible causesare:
R adefectiv ealternator
R atorn poly-V-belt
R amalfunct ioninthe electron ics
X Pull over andstop thevehicle safelyandswitch offthe engine,
paying attentiontoroad andtraffic conditions.
X Open thehood.
X Check whether thepoly-V-belt istorn .
If the poly-V- beltistorn:
! Donot cont inue driving. Theengine couldotherwise overheat.
X Consult aquali fiedspecialist workshop.
If the poly-V- beltisnot dam aged:
X Visit aquali fiedspecialist workshop. 4
Check
Engine Oil At
Next Refueling The
engine oillevel hasdropped tothe minimum level.
Aw arning tone also soun ds.
X Chec kthe engine oillevel atthe latest whennextrefueling
(Y page 313).
X Ifnecessary, addengine oil(Ypage 314).
X Ifengine oilneeds tobe added moreoften thanusual,have the
engine checkedataqual ified specialist workshop. Inform
ationonapproved engineoilscan beobtained fromanyqual ified specialist workshop
or on the Internet athttp: //www.mbusa.com (USAonly).
! The oillevel istoo low. Avoid longjourneys withtoolittle engine oil.There isarisk of
engine damage.
The displa ymessages andthecorresponding symbolthatindicate thattheoillevel istoo
low must notbeignored. 256
Display
messagesOn-board computer and displays

Disp
laymessa ges Poss
iblecauses/c onseq uences and M Solu
tions 8
Fue
lLev el Low The
fuellev elhas dropped into theres erveran ge.
X Refu elat thene ares tgas statio n. C Ther
eis on lyaver ysmal lamoun toffuel inthef uel tank.
X Refue lat thene ares tgas statio nwitho utfail. 8
Gas
CapLoos e The
fuel systempress ureistoo low. Thefuel filler capisnot clos ed
cor rectlyorthe fuel systemisleakin g.
X Check thatthefuel filler capiscor rectlyclos ed.
If th efuel filler capisnot corr ectly closed:
X Close thefuel filler cap.
If th efuel filler capiscorr ectly closed:
X Visit aqualified specialist workshop. 8
Ultr
aLow- sulfur Dies
elFuel Only Vehic
leswith adiesel engine: thefuel level hasfallen below the
reser verang e.
X Refuel atthe near estgas station .
X Only usecom merc iallyavailable vehicularULTRA -LOW SUL FUR
HIGH WAYDIES EL FUE L(ULS D,15 ppm SULFUR MAXIMUM ). ¸
Repl
aceAir Filter Vehic
leswith adiesel engine: theengineairfilterisdirt yand must
be replac ed.
X Visit aqualified specialist workshop. !
Chec
kFuel Filter Vehic
leswith adiesel engine: thereiswater inthe fuel filter. The
water mustbedrain edoff.
X Visit aqualified specialist workshop. Ø
Chec
k Addi
tive See
Oper
ator'sManu al The
DEFtan kis empt y.
X Have theDEFtank filledas soon asposs ibleataq ualifi ed
spec ialist workshop(Y page 152). Ø
Rem
aining Starts: 16 The
DEFlevel hasfallen toaminimum.
X Have theDEFtank filledimm ediat elyataqualifi edspec ialist
work shop.(Y page 152) Displ
aymes sages
257On-board computer and displays Z

Disp
laymessa ges Poss
iblecauses/c onseq uences and M Solu
tions DIS
TRONIC PLUS Cur
rently Una
vailableSee Ope
rator'sMan ual DI
ST RON ICisdeac tivat ed and tempo rarily inoper ative. Pos sible
caus esare:
R theDI ST RON ICPLU Sco ver intheradi atorgri lle isdir ty.
R fun ction isimp aire ddue toheav yrain orsnow.
R thesen sorsin thebump ersare dirty.
R therada rsensor system istempor arilyinoperat ive,e.g. due to
electr omagnet icradiation emittedbynearby TVorradio
stat ions orother sources ofelectr omagnet icradiation.
R the system isoutside theoperatin gtemper aturerange.
R The on-board voltage istoo low.
Aw arning tone also soun ds.
If th edispl aymes sage does notd isappear:
X Pull over andstop the vehic lesafely assoon aspossible ,paying
att ent ion toroad andtraffic conditio ns.
X Apply theelect ricpark ingbrak e.
X Clean theDISTRON ICPLUS coverinthe radiat orgrille
(Y page 322).
X Clean thebumper s(Y page 322).
X Restar tthe engine.
If the system detectsthat thesensors arefully operational, the
displa ymessage disappears.
DIS TRONIC isoperational again. DISTRONIC
PLUS Inoperative DIS
TRONIC PLUSisdefective. BASPLUS (Brake AssistPLUS) and
PRE-SA FE®
Brake maybeinoperative aswell.
Aw arning tone also soun ds.
X Visi taqu alified specialist workshop. DISTRO
NICPLUS Passiv
e You
have depressed theacceler atorpedal. DISTRONIC PLUSisno
longer controlling thespeed ofthe vehicle.
X Take yourfootoffthe acceler atorpedal. DISTRO
NICPLUS ---
mph An
activ ation condition forDIS TRONIC PLUSisnot fulfilled.
X Check theactiv ation condition sfor DIS TRONIC PLUS
(Y page 169). 262
Display
messagesOn-board computer and displays

Disp
laymessa ges Poss
iblecauses/c onseq uences and M Solu
tions h
Che
ck Tir
e Pre
ssure G
Ri
sk ofacci dent The
tire pre ssur ein on eor mor etires has dropped signific ant ly.
X Stop theveh iclewit hout makingany sudd ensteer ingor brak ing
man euve rs.P ay attentio ntothe traffic conditionsasyou doso.
X Ifnecessary, changeawheel (Ypage 374).
X Check thetire pressure. Ifnecessary, correctthe tire pressure
(Y page 359). h
Correct
Tire Pressure The
tirepressure istoo low inat least oneofthe tires orthe tire
pressure differencebetween thewheels istoo great.
X Check thetire pressures atthe next opportunit y.Ifnecessary,
correc tthe tire pressure (Ypage 359). Vehicle
Display
messages Possible
causes/conse quencesandM Solutions
Shift to 'P' or 'N'
to
Start Engine You
have attempt edtostart theengine withthetrans mission in
position Ror D.
X Shift thetrans mission toposition Por N. Auxiliary
Battery Malfunction The
auxilia rybattery forthe automatic transmission isno longer
being charged.
X Visit aquali fiedspecialist workshop atthe next opportunit y.
X Unt ilthen ,set the automatic transmission toposition Pbefore
you switch offthe engine.
X Before leaving thevehicle, applytheelectric parking brake. Apply
Brake to Shift
from'P' You
have attempt edtomove thetrans mission selector leverto
position D,Ror Nwithout depressing thebrake pedal.
X Depress thebrake pedal. Door
Open Vehicle
Notin'P' The
driver's doorisopen andthetrans mission isin position R,N
or D.
Aw arning tone also soun ds.
X Sh ift thetrans mis sion toposi tionP.
X Ap ply theelec tric park ingbrak e. Displ
aymes sages
265On-board computer and displays Z

Safety
systems Problem Possible
causes/co nsequences andM Solutions
$
(USAonly)
J (Canada only)
The redbrake system
warning lampcomes on
while theengine is
running. Awarning tone
also sounds. G
Risk
ofaccident The
brake boosting effectismalfunction ingand thebraking
characterist icsmay beaffected.
X Pull over andstop thevehicle safelyassoon aspossible, paying
atten tiontoroad andtraffic condition s.Do not cont inue driving
under anycircumst ances.
X Engage theelectric parking brake.
X Consult aqual ified specialist workshop.
X Observe theadditional displaymessages inthe multifunct ion
display . $
(USAonly)
J (Canada only)
The redbrake system
warning lampcomes on
while theengine is
running. Awarning tone
also sounds. G
Risk
ofaccident There
isnot enough brakefluidinthe brake fluidreservoir.
X Pull over andstop thevehicle safelyassoon aspossible, paying
atten tiontoroad andtraffic condition s.Do not cont inue driving
under anycircumst ances.
X Engage theelectric parking brake.
X Consult aqual ified specialist workshop immediately.
X Observe theadditional displaymessages inthe multifunct ion
display .
Do not add brake fluid.Thiswillnotrectify themalfunction . G
WARNING Driving
withthebrake warning lampilluminated canresult inan accident. Haveyourbrake system
check edimmediately ifthe brake warning lampstays on.Donot add brake fluidbefore checking
the brake system.
Overfilling thebrake fluidreservoir canresult inspilling brakefluidonhot engine partsandthe
brake fluidcatchin gfire. Youcanbeseriously burned. War
ning andindicator lampsin the instrum entcluster
271On-board computer and displays Z

Problem Possible
causes/co nsequences andM Solutions
å
The
yello wESP ®
OFF
warning lampislit while
the engine isrunning. G
Risk
ofaccident ESP
®
and ESP®
trailer stabilization aredeactivated. ESP®
will not
stabilize thevehicle ifit starts toskid orifawheel startstospin.
X Reactivate ESP®
.
Exc eptions: (Ypage 63).
X Adapt yourdriving styletosuit theroad andweather condition s.
If ESP ®
cannot beactivated:
X Have ESP®
check edataqual ified specialist workshop. ֌
The
yello wESP ®
and
ESP ®
OFF warning
lamps arelitwhile the
engine isrunning. G
Risk
ofaccident ESP
®
,BAS ,BAS PLUS, PRE-SA FE®
,PRE-SA FE®
Brake, theHOLD
funct ion,hillstart assist andESP®
trailer stabilization are
unavaila bledue toamalfunction .ESP ®
wi llnot stab ilize the vehicle
if it star tsto skid orifawh eel star tsto spi n.
The brakesystem continu estofuncti onnorma lly, bu tw itho utthe
func tionslist ed above.
ATT ENTION ASSIS Tis deact ivated.
X Obser vethe additio naldisplay messages inthe mult ifunc tion
display.
X Dr ive oncare fully.
X Visit aqualified specialist workshop. 274
Wa
rnin gand indica torlam psintheinstr ument clust erOn-board computer and displays

G
WARNING In
the event amalfu nction ofthe SRS isindica tedasoutli nedabove,the SRS may notbe
opera tional.
For yoursafet y,we stron gly recomm endthat you contactana uth oriz edMer cedes-Ben zCent er
immediately tohave thesystem checked.Other wisetheSRS may notbeactivat edwhen needed
in an acciden t,which couldresult inserious orfatal injury, oritmight deploy unexpec tedlyand
unnec essarily whichcouldalsoresult ininjury. Engine
Problem Possible
causes/consequences andM Solutions
;
The
yellow Check
En gine warning lamp
lights upwhile the
engine isrunn ing. There
maybeamalfunct ion,forexample:
R in the engine managemen t
R in the fuel injec tionsystem
R in the exhaust system
R in the ignition system(forvehicles withagasoline engine)
R in the fuel system
The emission limitvalues maybeexceeded andtheengine may
be runn inginemergen cymode.
X Have thevehicle checkedassoon aspossible ataqualified
specialist workshop. i
In
some states,you arerequired bylaw toimmediately visita
qualified specialist workshop assoon asthe yellow Check
En gine warning lamplights up.Ifin doubt, checkwhether such
legal regulations applyinthe state/prov inceinwhich youare
current lydriving. Vehicles
withadiesel engine: thefuel tank hasbeen rundry
(Y page 152).
X Start theengine threetofour times afterrefueling.
If the yellow Check Enginewarning lampgoesout,emergency
running modeiscanceled. Thevehicle neednotbecheck ed. 8
The
yellow reserve fuel
warning lampflashes
while thevehicle isin
motion. Inaddition, the
yell ow Check Engine
warning lamp;
may light up. The
fuel system pressure istoo low. Thefuel filler capisnot closed
correct lyor the fuel system isleaking.
X Observe theadditional displaymessages inthe multifunction
displa y.
X Check thatthefuel filler capiscorrect lyclosed.
X Ifthe fuel filler capisnot correctly closed:close thefuel filler
cap.
X Ifthe fuel filler capisclose d:visit aqual ified specialist
workshop. 276
War
ning andindicator lampsin the instrum entclusterOn-board computer and displays

Problem Possible
causes/co nsequences andM Solutions
?
The
redcoolant
warning lampcomes on
while theengine is
running. The
coolant levelistoo low.
If the coolant leveliscorrec t,the airflow tothe engine radiator
may beblocked orthe electric engineradiator fanmay be
malfunction ing.
The coolant istoo hotand theengine isno longer beingcooled
sufficiently.
X Observe theadditional displaymessages inthe multifunct ion
display .
X Pull over andstop thevehicle safelyandswitch offthe engine,
payi ngatten tiontoroad andtraffic condition s.
X Allow theengine andcoolant tocool.
X Check thecoolant levelandadd coolant (Ypage 315). Observe
the warning notes.
X Ifyou need toadd coolant moreoften thanusual,have the
engine coolant systemchecked.
X Make surethattheairsupply tothe engine radiator isnot
blocked, e.g.bysnow, slushorice.
X At coolant temperatures under248‡(120 †),drive tothe next
qualified specialist workshop.
X Avo idsubjec tingthe engin etoheavy loads, e.g.driving in
mountainous terrain,andstop- and-go traffic. ?
The
redcoolant
warning lampcomes on
while theengine is
runnin g.Awarning tone
also sounds. The
coolant temperat urehas exceeded 248‡(120 †).The
airflow tothe engine radiator maybeblocked orthe coolant level
may betoo low.
The engine isnot being cooled sufficient lyand may bedamaged.
X Observe theadditional displaymessages inthe multifunct ion
display .
X Pull over andstop thevehicle safelyandswitch offthe engine,
paying attentiontoroad andtraffic conditions.
X Allow theengine andcoolant tocool.
X Check thecoolant levelandadd coolant (Ypage 315). Observe
the warning notes.
X Ifyou need toadd coolant moreoften thanusual ,have the
en gin eco olan tsyst em checke d.
X Mak esur eth at theair supp lyto theen gin eradi ator isno t
bloc ked, e.g. by snow, slushor ice .
X At coolan ttemperatures under248‡(120 †),drive tothe next
qualified specialist workshop.
X Avo idsubjec tingthe engin etoheavy loads, e.g.driving in
mountainous terrain,andstop- and-go traffic. 278
War
ning andindicator lampsin the instru mentclusterOn-board computer and displays