workshop MERCEDES-BENZ M-Class 2012 W166 Service Manual

Useful
information
i This
Operat or'sManual describesall
models andallstan dard andoption al
equipment ofyour vehicle available atthe
time ofpublication ofthe Operat or's
Manual. Country-specificdiffer encesare
possible. Pleasenotethat your vehicle may
not beequipped withallfeature s
descr ibed. Thisalso applies tosafet y-
related systemsand func tions. i
Please
readtheinfor mation onqualified
specialist workshops(Ypage 25). Impor
tant safet ynotes You
willfind anillustrat ionofthe instrumen t
clust erinthe "Ataglance" section
(Y page 29). G
WARN
ING A
driver' satt ent ion tothe road andtraffic
con dition smust always behis/her primary
focus whendriving.
For your safetyand thesafet yof other s,
select ingfeature sthr ough themultifun ction
steer ingwheel should onlybedone bythe
driver whentrafficand road condition spermit
it to be done safely.
Bear inmind thatataspeed ofjust 30mph
(approxim ately50km/ h),your vehic leis
cove ringadistan ceof44 feet (approxim ately
14 m)every second. G
WARN
ING No
messages willbedisplayed ifeither the
inst rumen tclust eror the multif unction
display isinoper ative.
As aresult, youwillnotbeable tosee
info rmat ionabout yourdrivin gcon dition s,
such as
R speed
R outside temperatur e
R warnin g/indicato rlamps R
malf unction/ warn ingmes sages
R failur eof any systems
Dr ivin gch arac terist ics may beimpair ed.
If you must continue todriv e,do sowith added
caut ion.Contac tana uth oriz edMer cedes-
Ben zCent eras soon aspossible. G
WARN
ING Malfunct
ionand warning messages areonly
indicat edfor cert ainsystems andare
inten tionally notvery detailed. The
malfunct ionand warning messages are
simply areminder withrespect tothe
operation ofcert ainsystems. Theydonot
replace theowner's and/ordriver's
respons ibilitytomaint ainthe vehicle's
operatin gsafety. Haveallrequired
maint enanc eand safety checksperform edon
the vehicle. Bringthe vehicle toan authorized
Mercedes- BenzCenter toaddress the
malfunct ionand warning messages. Displays
andopera tion Coolant
temperaturedispla y G
WARN
ING Drivin
gwhen yourengine isoverheat edcan
cause somefluidswhich mayhave leaked into
the engine compart menttocatc hfire. You
could beseriously burned.
St eam from anoverheat edengine cancause
serious burnswhich canoccur justbyopening
the engine hood.Stay away fromtheengine
if you seeorhear steam comingfrom it.
St op the vehicle inasafe location awayfrom
other traffic.Turn offthe engine, getout ofthe
vehicle anddonot stand nearthevehicle until
the engine hascooled down.
The coolant temperaturegauge isin the
inst rument clusteronthe right- hand side.
Under normaloperatin gcon ditions andwith
the specified coolantlevel,thecoolant
temper aturemayriseto248 ‡(120 †). 222
Displays
andopera tionOn-board computer and displays

Safety
systems Display
messages Possible
causes/co nsequences andM Solutions
!÷
Currently
Unavailable
See Operator's
Manual G
Risk
ofaccident ABS
(Anti-lock Braking System), ESP®
(Electr onicStability
Program), BAS(Brake Assist), PRE-SAFE®
,the HOLD function,hill
start assist andESP®
trailer stabilization aretemporarily
unvailabl e.
BAS PLUS andPRE-SA FE®
Brake mayalsohave failed.
In addition, the÷, åand! warning lampslightupin
the instrumen tcluster.
The self-diagnosis functionmight notbecomplete, forexample.
ATTENTI ONASS ISTisdeactivated.
The brake system continues tofunct ionnormally, butwithout the
funct ionslisted above. Thewheels couldtherefore lockifyou
brake hard,forexample.
X Carefull ydrive asuitable distance makingslightsteering
movement sat aspeed above12mph (20km/ h).
If the display message disappears,the funct ionsment ioned
above areavaila bleagain.
If the display message continues tobe display ed:
X Drive oncarefully.
X Visit aqual ified specialist workshop. G
Risk
ofaccident ABS
,ESP ®
,BAS ,PRE-SA FE®
,the HOLD function,hillstart assist
and ESP®
trailer stabilization aretemporarily unavailable.
BAS PLUS andPRE-SA FE®
Brake mayalsohave failed.
In addition, the÷, åand! warning lampslightupin
the instrumen tcluster.
For example, theon-board voltagemaybeinsufficient .
ATTEN TIONASSISTisdeactivated.
The brake system continues tofunct ionnormally, butwithout the
funct ionslisted above. Thewheels couldtherefore lockifyou
brake hard,forexample.
X Drive oncarefully.
If the display message disappears,the funct ionsment ioned
above areavaila bleagain.
If the display message continues tobe display ed:
X Drive oncarefully.
X Visit aqual ified specialist workshop. Display
messages
239On-board computer and displays Z

Disp
laymessa ges Poss
iblecauses/c onseq uences and M Solu
tions !÷
Ino
perativeSee Ope
rator'sMan ual G
Ri
sk ofacci dent AB
S,ES P®
,BA S,PRE -SAF E®
,th eHO LD function ,hill start assi st
and ESP®
trailer stabiliz ation are unav ailable duetoamalf unction .
BA SPLU Sand PRE-SAF E®
Br ake may alsohavefail ed.
The $ (USAon ly)/ J (Canadaonly), ÷, å
and ! warning lamp sin theinst rum entc luster alsolight up.
The brak esyst emcontinues tofun ction normally, butwitho utthe
func tionslist ed above. Thewheels couldtherefore lock ifyou
brak ehard, forexam ple.
ATT ENTION ASSIS Tis deact ivated.
X Dr ive oncare fully.
X Visit aqualified specialist workshop immed iately. ÷
Curr
ently Unav
ailableSee Oper
ator'sManu al G
Risk
ofacciden t ES
P®
,BA S,PRE- SAFE®
,the HOL Dfunc tion,hill start assist and
ES P®
trailer stabilizat ionare tem porar ilyunavailable.
BA SPLUS andPRE- SAFE®
Br ake may alsohave failed.
In additio n,the ÷ andå warnin glamps lightupinthe
inst rumen tclust er.
The self- diagno sisfunc tion might notbecom plete ,for exam ple.
ATT ENTION ASSIS Tis deact ivated.
The brak esyst emcontinues tofun ction normally, butwitho utthe
func tionslist ed above.
X Carefully driveasuitable distancemak ingslight steerin g
mov emen tsat aspeed above12mph (20km/h).
If the display messagedisappears ,the func tionsmen tioned
above areavailable again.
If the display messagecontinues tobe displayed:
X Dr ive oncare fully.
X Visit aqualified specialist workshop. 240
Display
messagesOn-board computer and displays

Disp
laymessa ges Poss
iblecauses/c onseq uences and M Solu
tions ÷
Ino
perative See Ope
rator'sMan ual G
Ri
sk ofacci dent ES
P®
,BA S,PRE -SAF E®
,th eHO LD function ,hill start assi stand
ES P®
trailer stabiliz ation are unav ailable duetoamalf unction .
BA SPLU Sand PRE-SAF E®
Br ake may alsohavefail ed.
In addit ion,th e÷ andå warning lamp sligh tupin the
inst rument cluster.
ATTE NTION ASSIS Tis deactiv ated.
The brake system continues tofunc tion norm ally,butwithout the
func tionslisted above.
X Driv eon carefully.
X Visit aqualified specialist workshop. T!
÷
Inoper
ative See Operat
or'sManual G
Risk
ofaccident EB
D(elect ronic brake forcedistr ibution), ABS,ES P®
,BA S,PRE-
SA FE®
,the HOLD function,hill start assist andESP®
trailer
stabilizat ionare unavailable duetoamalfunc tion.
BA SPLUS andPRE-S AFE®
Brak emay alsohave failed.
In addition, the÷, åand! warning lampslightupin
the instrument clusterandawarning tonesounds.
ATTE NTION ASSIS Tis deactiv ated.
The brake system continues tofunc tion norm ally,butwithout the
func tionslisted above. Thewheels couldtherefore lockifyou
brake hard,forexample.
X Driv eon carefully.
X Visit aqualified specialist workshopimmediately. #
Check
Brake Pad Wear The
brake pads/linin gshave reached theirwear limit.
X Visit aqualified specialist workshop. F(USA
only)!
(Canada
only) Please
Release Parkin
gBrake The
redF (USAonly)/ !(Canada only)indicat orlamp
flashes andawarning tonesounds. Acondition forautomatic
release ofthe electric parking brakeisnot fulfilled (Ypage 156).
You aredriving withtheelectric parking brakeapplied .
X Release theelectric parking brakemanually . The
redF (USAonly)/ !(Canada only)indicator lamp
flashes andawarning tonesounds.
You aremaking anemergenc ystop using theelectric parking
brake (Ypage 156). Display
messages
241On-board computer and displays Z

Disp
laymessa ges Poss
iblecauses/c onseq uences and M Solu
tions F(U
SA
on ly)!(Can ada
on ly) Par
kingBra keSee Ope
rator'sMan ual The
yello w! warning lamp lightsup.
The electric park ing brak eis malf unction ing.
To apply:
X Swi tchof fth eign ition .
X Pre sstheelec tric park ingb rake handl efor atlea st10 seconds.
X Shift thetransmissi ontoP.
X Consu ltaqua lified speci alist workshop . The
yellow ! warning lampandthered F (USA
only )/! (Canada only)indica torlamp light up.
The electric parking brakeismalfu nctioning.
To rele ase:
X Switch offthe ignitio nand turn itback on.
X Rel ease theelectric parking brakemanua lly.
or
X Rel ease theelectric parking brakeautomatical ly(Y pag e156).
If the yellow ! warning lampremai nslitor continues toflas h:
X Do not drive on.
X Consu ltaqua lified speci alist workshop . The
redF (USAonly)/! (Canada only)indica torlamp
flas hes and theyellow ! warning lamplights up.
The electric parking brakeismalfu nctioning.
To rele ase:
X Switch offthe ignitio nand turn itback on.
X Rel ease theelectric parking brakemanua lly.
To apply:
X Switch offthe ignitio nand turn itback on.
X Apply theelectric parking brakemanua lly.
If the red
F (USA
only)/
! (Ca
nada only)indica torlamp
continues toflas h:
X Do not drive on.
X Secure thevehicl eaga inst rolling away (Ypag e334).
X Shift thetransmissi ontoP.
X Turn thefront wheelstoward sthe curb.
X Consu ltaqua lified speci alist workshop . 242
Di
splay messag esOn-board computer and displays

Disp
laymessa ges Poss
iblecauses/c onseq uences and M Solu
tions The
yello w! warning lamp lightsup. The redF (USA
on ly)/ ! (Canadaonly) indic ato rlamp flashes for
appro ximately10 sec onds aftertheelec tric park ingbrak ehas
been applied orrele ased. Itth en goes outorrem ains lit.
The electric park ingbrak eis malf unctionin g.
X Swit choff theign ition and turnit back on.
X En gage theelec tric park ingbrak e.
If it is no tp ossible toengage theelectric parking brake:
X Shift thetrans mission toP.
X Visit aquali fiedspecialist workshop.
If it is not possible torelease theelectric parking brake:
X Release theelectric parking brakeautomatically (Ypage 156).
If the electric parking brakestillcann otbe released:
X Consult aquali fiedspecialist workshop. The
yellow !warning lamplights up.When yourelease orapply
the electric parking brakemanually ,the red F (USA
only)/ !(Canada only)indicator lampflashes.
The electric parking brakeismalfunct ioning.Itis not possible to
apply theelectric parking brakemanually .
X Shift thetrans mission toP.
X Visit aquali fiedspecialist workshop. F(USA
only)!(Canada
only) Pkg
Brake Inoperative The
yellow !warning lamplights up.The redF (USA
only)/ !(Canada only)indicator lampflashes for
approximately 10seconds aftertheelectric parking brakehas
been applied orreleased. Itthen goes outorremains lit.
The electric parking brakeismalfunct ioning,e.g.because of
overvoltage orundervoltage.
X Remove thecause forthe overvoltage orundervoltage, e.g.by
charging thebattery orrestart ingthe engine.
X En gage orrelease theelectric parking brake.
If it remains impossible toapply orrelease theelectric parking
brake:
X Switch offthe ignition andturn itback on.
X En gage orrelease theelectric parking brake.
If the electric parking brakestillcann otbe released:
X Consult aquali fiedspecialist workshop. Display
messages
243On-board computer and displays Z

Disp
laymessa ges Poss
iblecauses/c onseq uences and M Solu
tions The
displaymes sage ison lysho wnwhile theveh icleis in mot ion.
The yello w! warning lamp lightsup and thered F (USA
on ly)/ ! (Canadaonly) indic ato rlamp flashes.
It is no tp ossible toapply theelectric parking brakemanually .
X Shift thetrans mission toP.
X Visit aquali fiedspecialist workshop. F(USA
only)!(Canada
only)
Turn
Onthe Ignition
to Release
the Parking
Brake The
redF (USAonly)/ !(Canada only)indicator lamplights
up.
You attempt edtorelease theelectric parking brakewhilethe
ignition wasswitched off.
X Smar tKey: turntheSmart Keytoposition 1in the ignition lock.
X KEYL ESS-GO: switchonthe ignition. $(USA
only)J(Canada
only)
Check
BrakeFluid Level G
Risk
ofaccident There
isnot enough brakefluidinthe brake fluidreservoir.
Additionally, thered $ (USAonly)/ J(Canada only)
warning lamplights upinthe instr ument cluster andawarning
ton esounds.
X Pull over andstop thevehicle safelyassoon aspossible, paying
atten tiontoroad andtraffic conditions.Donot cont inue driving
under anycircumst ances.
X En gage theelectric parking brake.
X Consult aquali fiedspecialist workshop.
X Do not add brake fluid.Thiswillnotrect ifythe malfunct ion. G
WARNIN
G Drivin
gwith themessage Check Brake Fluid Level display
edcan result inan accident .Have
your brakesyst emcheck edimm ediat ely.
Do notadd brake fluidbefore checkingthe brake system. Overfillingthebrake fluidreserv oircan
result inspilling brakefluidonhot engin eparts andthebrake fluidcatching fire.Youcanbe
seriously burned. 244
Display
messagesOn-board computer and displays

Disp
laymessa ges Poss
iblecauses/c onseq uences and M Solu
tions G
Tel
eAid Ino
perative US
Ao nly:one ormor eof the mainfunctio nsinthe mbr ace system
ar ema lfunctio ning.
Ca nad aonl y:one ormor eof the mainfunctio nsofthe TELEAI D
sy stem arema lfunctio ning.
X USA only:ha ve the mbr ace system checked ataq ualifi ed
spec ialist workshop.
X Canad aon ly: have theTE LE AIDs ystem checke dat aqualif ied
spe cialist wor kshop . PRE
-SAFE Ino
perative See Ope
rator'sMan ual G
Ri
sk ofinjury Im
por tant fun ction sofPRE-SAFE ®
have failed .Alloth erocc upant
safet ysyst ems, e.g.airbags, remain available.
X Visit aqualified specialist workshop immed iately. PRE-
SAFE Func
tion Curr
ently Limi
tedSee Oper. Manu
al G
Risk
ofacciden t PRE-
SAFE®
Br ake istem porar ilyinope rative if:
R the DISTRON ICPLUS coverinthe radiat orgrill isdirt y.
R the sensors inthe bumper sare dirty.
R its func tion isimpaired duetoheavy rainorsno w.
R the radar sensor syst emistem porar ilyinope rative, e.g. due to
elect romagnet icradiat ionemit tedbynear byTV orradio
st ation sor oth ersourc esofelect romagnet icradiat ion.
R the syst emisouts idethe operat ingtem perat urerang e.
R the on-board voltage istoo low.
PRE- SAFE®
Br ake isoperat ionalagain andthedisplay message
disappears if:
R the dirt (e.g.slush) drops awaywhile thevehic leisin mot ion.
R the syst emdete ctsthat thesensors arefully available again.
R the syst emiswithin theoperat ingtem perat urerang e.
If the display messagecontinues tobe displayed:
X Clean theDISTRON ICPLUS coverinthe radiat orgrill
(Y page 322).
X Clean thebumper s(Y page 322).
X Restar tthe engine.
X Wait untilthebattery issufficiently charged. Display
messages
245On-board computer and displays Z

Disp
laymessa ges Poss
iblecauses/c onseq uences and M Solu
tions PRE
-SAFE Fun
ctions Limited See
Operator's Man
ual G
Ri
sk ofacci dent PRE
-SAF E®
Br ake isdef ective. BASPLU Sor thed istanc ewarning
sign almay alsohave failed.
X Visi taqu alified specialist workshop. 6
SRS
Malfun ction Servic
eRequir ed G
Risk
ofinjur y There
isamalfunc tioninthe SRS (Supplemen talRestrain t
Syst em). The6 warning lampalsolights upinthe instrument
cluster .
X Visit aqualified specialist workshop. 6
Front
LeftSRS Malfun
ction Servic
eRequir ed or
Front
Right Malfun
ction Servic
eRequir ed G
Risk
ofinjur y SRS
hasmalfunc tionedatthe fron ton the left orright .The 6
warning lampalsolights upinthe instrument cluster.
X Visit aqualified specialist workshop. 6
Rear
LeftSRS Malfun
ction Servic
eRequir ed or
Rear
Right SRS Malfun
ction Servic
eRequir ed G
Risk
ofinjur y SRS
hasmalfunc tionedatthe rear onthe left orright .The 6
warning lampalsolights upinthe instrument cluster.
X Visit aqualified specialist workshop. 6
Rear
Center SRS Malfun
ction Servic
eRequir ed G
Risk
ofinjur y SRS
hasmalfunc tionedatthe rear center. The 6 warning lamp
also lights upinthe instrument cluster.
X Visit aqualified specialist workshop. 6
Left
SideCurtai n Airbag Malfun
ction Servic
eRequir ed or
Right Side Curtai
n Airbag Malfun
ction Servic
eRequir ed G
Risk
ofinjur y There
isamalfunc tioninthe left- hand and/or right-handwindow
curt ainairbag. The6 warning lampalsolights upinthe
inst rument cluster.
X Visit aqualified specialist workshop. 246
Display
messagesOn-board computer and displays

Disp
laymessa ges Poss
iblecauses/c onseq uences and M Solu
tions X
Vis itaqualif iedspecialist wor kshop immediat ely. G
WAR
NING If
th e45 indic ato rlamp remains offeven afterperf ormingtheabove correctivest eps, do
no th ave any childre n12years oldand under andother smallindividuals usethefron t-passenger
seat until thesystem hasbeen repaired. Display
messages Possible
causes/consequences andM Solutions
Front
Passeng er Airbag
Disabl' d See
Operato r's Manual The
front-passenger airbag isdeactivat edduring thejourn eyeven
though anadult oraperson largerthanacert ainsize isoccupying
the fron t-passenger seat.Ifadditional forcesare applied tothe
seat, thesystem mayinterpret theoccupant 'sweight aslower
than itactually is.
X Pull over andstop thevehicle safelyassoon aspossible, paying
atten tiontoroad andtrafficcon ditions .
X En gage theparking brake.
X Switc hoff the ignition .
X Have theoccupant getout ofthe vehicle.
X Keep theseat unocc upied, closethefron t-passenger doorand
switch onthe ignition .
Observe the45(Y page44)indicat orlamp andthe
multifunc tiondisplay andchec kthe following:
Seat unoccupied andignition switched on:
R the 45 indicatorlampmust lightupand remain lit.When
the indicator lampison, OCS (Ypage 44)has deactivated the
front -passenger airbag.
R the Front
Passenger AirbagEnabled SeeOperator's Manual or Front
Passenger AirbagDisabled See Operator's
Manual displa
ymessages mustnotappea rint he
multifunction display.Wait foraperiod ofat least 60seconds
until thenecessary systemcheckshave been completed andto
make surethatthedispla ymessages donot appea rint he
multifunction display.
If these condition sare fulfilled ,the front -passenger seatcanbe
occupied again.Whether the45 indicatorlampremains lit
or goes outdepends onhow OCS classifies theoccupant.
If the condition sare not fulfilled ,the system isnot operating
correct ly.
X Visit aqual ified specialist workshop immediately. Display
messages
249On-board computer and displays Z