check engine MERCEDES-BENZ M-Class 2015 W166 Owner's Guide

G
WARNING
Flammable materials introduced through
environmental influence or by animals can
ignite if in contact with the exhaust system or parts of the engine that heat up. There is a risk
of fire.
Carry out regular checks to make sure that
there are no flammable foreign materials in
the engine compartment or in the exhaust
system.
! Do not depress the accelerator when
starting the engine.
General notes i
Vehicles with a gasoline engine:
the
catalytic converter is preheated for up to
30 seconds after a cold start. The sound of the engine may change during this time.
Automatic transmission X
Shift the transmission to position P
(Y page 168).
The transmission position display in the
multifunction display shows
P (Y page 168).
i You can start the engine in transmission
position Pand N.
Starting procedure with the SmartKey X
To start a gasoline engine: turn the
SmartKey to position 3in the ignition lock
(Y page 157) and release it as soon as the
engine is running.
X To start a diesel engine: turn the Smart-
Key to position 2in the ignition lock
(Y page 157).
The 0028 preglow indicator lamp in the
instrument cluster lights up.
X When the 0028preglow indicator lamp
goes out, turn the SmartKey to position 3
(Y page 157) and release it as soon as the
engine is running. i
You can start the engine without preglow
if the engine is warm.
Using KEYLESS-GO to start the engine X
Depress the brake pedal and keep it
depressed.
X To start a gasoline engine: press the
Start/Stop button (Y page 158) once.
The engine starts.
X To start a diesel engine: press the Start/
Stop button once (Y page 158).
Preglow is activated and the engine starts.
i The Start/Stop button can be used to
start the vehicle without inserting the
SmartKey into the ignition lock. The Start/
Stop button must be inserted in the ignition
lock and the SmartKey must be in the vehi-
cle. This mode for starting the engine oper-
ates independently of the ECO start/stop
automatic engine start function. Pulling away
Automatic transmission G
WARNING
If the engine speed is above the idling speed
and you engage transmission position Dor R,
the vehicle could pull away suddenly. There is a risk of an accident.
When engaging transmission position Dor R,
always firmly depress the brake pedal and do not simultaneously accelerate.
X Depress the brake pedal and keep it
depressed.
X Shift the transmission to position Dor R
(Y page 168).
X Release the brake pedal.
X Carefully depress the accelerator pedal.
The electric parking brake (Y page 184) is
automatically released. 160
DrivingDriving and parking

Problems with the engine
Problem
Possible causes/consequences and
0050
0050Solutions The engine does not
start. The starter motor
can be heard. R
There is a malfunction in the engine electronics.
R There is a malfunction in the fuel supply.
X Before attempting to start the engine again, turn the SmartKey
in the ignition back to position 0or press the Start/Stop button
repeatedly until all indicator lamps in the instrument cluster go out.
X Try to start the engine again (Y page 159). Avoid excessively
long and frequent attempts to start the engine as these will drain
the battery.
If the engine does not start after several attempts:
X Consult a qualified specialist workshop. The engine does not
start. You cannot hear
the starter motor. The on-board voltage is too low because the battery is too weak or
discharged.
X Jump-start the vehicle (Y page 391).
If the engine does not start despite attempts to jump-start it:
X Consult a qualified specialist workshop. The starter motor was exposed to a thermal load that was too high.
X Allow the starter motor to cool down for approximately two
minutes.
X Try to start the engine again.
If the engine still does not start:
X Consult a qualified specialist workshop. Vehicles with a gaso-
line engine:
The engine is not run-
ning smoothly and is
misfiring. There is a malfunction in the engine electronics or in a mechanical
component of the engine management system.
X Only depress the accelerator pedal slightly.
Otherwise, non-combusted fuel may get into the catalytic con-
verter and damage it.
X Have the cause rectified immediately at a qualified specialist
workshop. The coolant tempera-
ture gauge shows a
value above 248 ‡
(120 †). The coolant level is too low. The coolant is too hot and the engine
is no longer being cooled sufficiently.
X Stop as soon as possible and allow the engine and the coolant to
cool down.
X Check the coolant level (Y page 369). Observe the warning
notes as you do so and add coolant if necessary. Driving
167Driving and parking Z

Automatic transmission
Important safety notes
G
WARNING
If the engine speed is above the idling speed
and you engage transmission position Dor R,
the vehicle could pull away suddenly. There is a risk of an accident.
When engaging transmission position Dor R,
always firmly depress the brake pedal and do not simultaneously accelerate. G
WARNING
The automatic transmission switches to neu-
tral position Nwhen you switch off the engine.
The vehicle may roll away. There is a risk of an
accident.
After switching off the engine, always switch
to parking position P. Prevent the parked vehi-
cle from rolling away by applying the parking
brake. DIRECT SELECT lever
Overview of transmission positions 005D
Park position with parking lock
005E Reverse gear
005C Neutral
005B Drive
The DIRECT SELECT lever is on the right of the
steering column.
i The DIRECT SELECT lever always returns
to its original position. The current trans- mission position
P,R, Nor Dappears in the
transmission position display (Y page 168)
in the multifunction display.
Transmission position and drive pro-
gram display !
If the transmission position display in the
multifunction display is not working, you
should pull away carefully to check whether the desired transmission position is
engaged. Ideally, you should select trans-
mission position Dand, in AMG vehicles,
drive program Cor S. Transmission position and drive program display
0043 Transmission position display
0044 Drive program display
The current transmission position and drive
program appear in the multifunction display.
i The arrows in the transmission position
display show how and into which transmis-
sion positions you can change using the
DIRECT SELECT lever.
Engaging park position P !
If the engine speed is too high or the vehi-
cle is moving, do not shift the automatic
transmission directly from Dto R, from Rto
D or directly to P. The automatic transmis-
sion could otherwise be damaged. 168
Automatic trans
missionDriving and parking

R
If the electric parking brake is engaged,
release it.
R Switch off the ignition and leave the Smart-
Key in the ignition lock.
Using KEYLESS-GO:
R Make sure that the ignition is switched on.
R When the vehicle is stationary, depress the
brake pedal and keep it depressed.
R Engage park position P.
R Release the brake pedal.
R Remove the Start/Stop button from the
ignition lock.
R Insert the SmartKey into the ignition lock.
R Switch on the ignition.
R Depress the brake pedal and keep it
depressed.
R Shift to neutral N.
R Release the brake pedal.
R If the electric parking brake is engaged,
release it.
R Switch off the ignition and leave the Smart-
Key in the ignition lock.
Engaging drive position D X
If the transmission is in position Ror N:
push the DIRECT SELECT lever down past
the first point of resistance.
X If the transmission is in position P: depress
the brake pedal and push the DIRECT
SELECT lever down past the first point of
resistance. Transmission positions
0045 Park position
Do not shift the transmission into
position
P(Y page 182) unless the
vehicle is stationary. The parking
lock should not be used as a brake when parking. Always apply the
electronic parking brake in addi-
tion to the parking lock in order to
secure the vehicle.
If the vehicle electronics are mal-
functioning, the transmission may
be locked in position P. Have the
vehicle electronics checked imme-
diately at a qualified specialist
workshop.
The automatic transmission shifts
to Pautomatically if you:
R remove the SmartKey
R switch off the engine when in R
or Dand open one of the front
doors 0046 Reverse gear
Only shift the transmission to
R
when the vehicle is stationary. 170
Automatic transmissionDriving and parking

Problems with the transmission
Problem
Possible causes/consequences and
0050
0050Solutions The transmission has
problems shifting gear. The transmission is losing oil.
X Have the transmission checked at a qualified specialist work-
shop immediately. The acceleration ability
is deteriorating.
The transmission no
longer changes gear. The transmission is in emergency mode.
It is only possible to shift into
secondgear and reverse gear.
X Stop the vehicle.
X Shift the transmission to position P.
X Switch off the engine.
X Wait at least ten seconds before restarting the engine.
X Shift the transmission to position Dor R.
If D is selected, the transmission shifts into secondgear; ifRis
selected, the transmission shifts into reverse gear.
X Have the transmission checked at a qualified specialist work-
shop immediately. Transfer case
! Performance tests may only be carried
out on a 2-axle dynamometer. The brake
system or transfer case could otherwise be
damaged. Contact a qualified specialist
workshop for a performance test.
! Because ESP ®
is an automatic system,
the engine and ignition must be switched
off (SmartKey in position 0or 1or Start/
Stop button in position 0or 1) when the
electric parking brake is being tested on a
brake dynamometer (maximum
10 seconds).
Braking triggered automatically by ESP ®
may seriously damage the brake system.
! Vehicles with 4MATIC must not be towed
with either the front or the rear axle raised,
as doing so will damage the transmission.
This section is only valid for vehicles with 4-
wheel drive (4MATIC). Power is always trans- mitted to both axles. Refueling
Important safety notes
G
WARNING
Fuel is highly flammable. If you handle fuel
incorrectly, there is a risk of fire and explo-
sion.
You must avoid fire, open flames, creating
sparks and smoking. Switch off the engine
and, if applicable, the auxiliary heating before refueling. G
WARNING
Fuel is poisonous and hazardous to health.
There is a risk of injury.
You must make sure that fuel does not come into contact with your skin, eyes or clothing
and that it is not swallowed. Do not inhale fuel
vapors. Keep fuel away from children. Refueling
177Driving and parking
Z

Opening the fuel filler flap
0043
To open the fuel filler flap
0044 To insert the fuel filler cap
0087 Fuel type to be used
0085 Tire pressure table
X Switch the engine off.
X Remove the SmartKey from the ignition
lock.
X KEYLESS-GO: open the driver’s door.
This corresponds to key position 0: "key
removed".
The driver’s door can be closed again.
X Press the fuel filler flap in the direction of
arrow 0043.
The fuel filler flap swings up.
X Turn the fuel filler flap counter-clockwise
and remove it.
X Insert the fuel filler cap into the holder
bracket on the inside of filler flap 0044.
X Completely insert the filler neck of the fuel
pump nozzle into the tank, hook in place
and refuel.
X Only fill the tank until the pump nozzle
switches off.
i Vehicles with a diesel engine: the filler
neck is designed for refueling at diesel fill-
ing pumps.
i Do not add any more fuel after the pump
stops filling for the first time. Otherwise,
fuel may leak out. Closing the fuel filler flap X
Replace the cap on the filler neck and turn
clockwise until it engages audibly.
X Close the fuel filler flap.
i Close the fuel filler flap before locking the
vehicle.
i If you are driving with the fuel filler cap
open, the 00B6reserve fuel warning lamp
flashes.
In addition, the 00B9Check Engine warning
lamp may light up (Y page 327).
A message appears in the multifunction
display (Y page 302).
For further information on warning and indi-
cator lamps in the instrument cluster, see
(Y page 327). Refueling
179Driving and parking Z

Problems with fuel and the fuel tank
This section provides descriptions of and solutions to safety-relevant problems. Descriptions
of and solutions to further problems can be found in the Digital Operator's Manual. Problem
Possible causes/consequences and
0050
0050Solutions Fuel is leaking from the
vehicle. The fuel line or the fuel tank is faulty.
G WARNING
Risk of explosion or fire. X Turn the SmartKey to position 0in the ignition lock and remove
it immediately (Y page 157).
X Do not restart the engine under any circumstances.
X Consult a qualified specialist workshop. DEF (BlueTEC vehicles only)
Important notes on use To function properly, BlueTEC exhaust gas
aftertreatment must be operated with the
reducing agent DEF. Adding DEF is one of the
tasks performed during maintenance. Under
normal operating conditions, a tank of DEF
lasts until the next service due date.
When the supply of DEF is almost used up, the
Check
Check Additive
Additive See SeeOperator's
Operator's Manual
Manual
message is shown in the multifunction dis-
play.
If you drive the vehicle faster than 10 mph
(16 km/h), the Check
Check Additive Additive See
SeeOper‐
Oper‐
ator's Manual
ator's Manual message goes out after
approximately one minute.
When the supply of DEF is down to a reserve
of approximately 1 gal (3.8 l) the Refill Refill
AdBlue/DEF
AdBlue/DEF See
SeeOperator's
Operator's Manual
Manualmes-
sage is shown in the multifunction display.
When the DEF supply drops to a minimum, the Remaining Starts: 16
Remaining Starts: 16 message is shown
in the multifunction display.
If the Refill AdBlue/DEF No Start in Refill AdBlue/DEF No Start in
XXXX km XXXX km message is shown in the multifunc-
tion display, you can still drive the vehicle
over the distance shown. If DEF is not refilled,
you will subsequently be unable to start the
engine. If the Refill AdBlue/DEF Eng.
Refill AdBlue/DEF Eng. Start Not Poss Start Not Poss
message appears in the
multifunction display and the engine does not
start, you must add DEF.
X Add at least 1 gal (3.8 l)of DEF.
X Switch on the ignition for at least 60 sec-
onds.
X Start the engine.
i Have the DEF tank refilled at a qualified
specialist workshop.
Use the special DEF refill bottle when adding DEF between maintenance intervals. Contact
an authorized Mercedes-Benz Center with
any questions or, if necessary, contact Road-
side Assistance (Y page 26).
If the outside temperature is below 12 ‡
(00F811 †) it may be difficult to top up. If DEF is
frozen and there is an active warning indica-
tor, it may not be possible to add DEF. Park
the vehicle in a warmer place, e.g. in a garage,
until DEF has become fluid again. It will then
be possible to add DEF again. Alternatively,
have the DEF tank refilled at a qualified spe-
cialist workshop.
Further information about BlueTEC exhaust
gas aftertreatment and DEF is available at any
authorized Mercedes-Benz Center. 180
RefuelingDriving and parking

Servicing the brakes
!
If the red brake warning lamp lights up in
the instrument cluster and you hear a warn- ing tone while the engine is running, the
brake fluid level may be too low. Observe
additional warning messages in the multi-
function display.
The brake fluid level may be too low due to brake pad wear or leaking brake lines.
Have the brake system checked immedi-
ately. This work should be carried out at a
qualified specialist workshop.
! A function or performance test should
only be carried out on a 2-axle dynamom-
eter. If you are planning to have the vehicle tested on such a dynamometer, contact an
authorized Mercedes-Benz Center to
obtain further information first. Otherwise,
you could damage the drive train or the
brake system.
! Because ESP ®
is an automatic system,
the engine and ignition must be switched
off (SmartKey in position 0or 1or Start/
Stop button in position 0or 1) when the
electric parking brake is being tested on a
brake dynamometer (maximum
10 seconds).
Braking triggered automatically by ESP ®
may seriously damage the brake system.
All checks and maintenance work on the
brake system must be carried out at a quali-
fied specialist workshop. Consult a qualified
specialist workshop to arrange this.
Have brake pads installed and brake fluid
replaced at a qualified specialist workshop.
If the brake system has only been subject to
moderate loads, you should test the function- ality of your brakes at regular intervals. To doso, depress the brake pedal firmly when driv-
ing at a high speed. This improves the grip of
the brake pads.
You can find a description of Brake Assist
(BAS) on (Y page 68) or of BAS PLUS on
(Y page 69). Mercedes-Benz recommends that you only
have brake pads/linings installed on your
vehicle which have been approved for
Mercedes-Benz vehicles or which correspond
to an equivalent quality standard. Brake
pads/linings which have not been approved
for Mercedes-Benz vehicles or which are not
of an equivalent quality could affect your vehi-
cle's operating safety.
Mercedes-Benz recommends that you only
use brake fluid that has been specially
approved for your vehicle by Mercedes-Benz,
or which corresponds to an equivalent quality standard. Brake fluid which has not been
approved for Mercedes-Benz vehicles or
which is not of an equivalent quality could
affect your vehicle's operating safety.
High-performance brake system for
AMG vehicles The high-performance brake system is only
available on AMG vehicles.
The high-performance brake system is
designed for heavy loads. This may lead to
noise when braking. This will depend on:
R speed
R braking force
R environmental conditions, such as temper-
ature and humidity
The wear of individual components of the
brake system, such as the brake pads/linings
or brake discs, depends on the individual driv-
ing style and operating conditions.
For this reason, it is impossible to state a
mileage that will be valid under all circum-
stances. An aggressive driving style will lead
to high wear. You can obtain further informa- tion about this from your authorized
Mercedes-Benz Center.
New and replaced brake pads and discs only
reach their optimum braking effect after sev-
eral hundred kilometers of driving. Compen-
sate for this by applying greater force to the
brake pedal. Keep this in mind, and adapt Driving tips
189Driving and parking Z

your driving and braking accordingly during
this break-in period.
Excessive heavy braking results in corre-
spondingly high brake wear. Observe the
0026 brake wear warning lamp in the instru-
ment cluster and note any brake status mes-
sages in the multifunction display. Especially
for high performance driving, it is important to maintain and have the brake system checkedregularly. Driving on wet roads
Hydroplaning If water has accumulated to a certain depth
on the road surface, there is a danger of
hydroplaning occurring, even if:
R you drive at low speeds.
R the tires have adequate tread depth.
For this reason, in the event of heavy rain or in
conditions in which hydroplaning may occur,
you must drive in the following manner:
R lower your speed.
R avoid ruts.
R avoid sudden steering movements.
R brake carefully.
Driving on flooded roads !
Do not drive through flooded areas.
Check the depth of any water before driving through it. Drive slowly through standing
water. Otherwise, water may enter the
vehicle interior or the engine compartment.
This can damage the electronic compo-
nents in the engine or the automatic trans- mission. Water can also be drawn in by the
engine's air suction nozzles and this can
cause engine damage.
i Vehicles with the AIRMATIC package:
set the raised level before driving through
standing water. Off-road fording !
Under no circumstances should you
accelerate before entering the water. The
bow wave could cause water to enter and
damage the engine and other assemblies.
! Do not open any of the vehicle's doors
while fording. Otherwise, water could get
into the vehicle interior and damage the
vehicle's electronics and interior equip-
ment.
R Establish how deep the water is and the
characteristics of the body of water before
fording.
R Vehicles with the AIRMATIC package:
select the highest possible vehicle level.
R Shift to a lower gear using the left-hand
steering wheel paddle shifter.
R Avoid high engine speeds.
R Enter and exit the water at a flat place and
at a steady walking pace.
R Drive slowly and at an even speed through
the water.
R Do not stop.
R Water offers a high degree of resistance,
and the ground is slippery and in some
cases unstable. Therefore, it is difficult and
dangerous to pull away in the water.
R Ensure that a bow wave does not form as
you drive.
R Clean any mud from the tire tread after
fording.
R Apply the brakes to dry them after fording.
Always observe the fording depth values
(Y page 457). Winter driving
G
WARNING
If you shift down on a slippery road surface in an attempt to increase the engine's braking
effect, the drive wheels could lose their grip.
There is an increased danger of skidding and
accidents. 190
Driving tipsDriving and pa
rking

Do not shift down for additional engine brak-
ing on a slippery road surface. G
DANGER
If the exhaust pipe is blocked or adequate
ventilation is not possible, poisonous gases
such as carbon monoxide (CO) may enter the vehicle. This is the case, e.g. if the vehicle
becomes trapped in snow. There is a risk of
fatal injury.
If you leave the engine or the auxiliary heating
running, make sure the exhaust pipe and area
around the vehicle are clear of snow. To
ensure an adequate supply of fresh air, open a window on the side of the vehicle that is not
facing into the wind.
Have your vehicle winter-proofed at a quali-
fied specialist workshop at the onset of win-
ter.
Drive particularly carefully on slippery road
surfaces. Avoid sudden acceleration, steering and braking maneuvers. Do not use the cruise
control or DISTRONIC PLUS.
If the vehicle threatens to skid or cannot be
stopped when moving at low speed:
X Shift the transmission to position N.
Vehicles with the ON&OFFROAD package:
if driving in snow or with snow chains, select
the snow program (Y page 248) with the off-
road program selector wheel in the center
console.
i Vehicles with a diesel engine:
do not
cover the radiator, e.g. with a protective
cover. The measuring function of the
onboard diagnosis system may otherwise
provide inaccurate values. Some of these
values are required by law and must there-
fore always be accurate.
The outside temperature indicator is not
designed to serve as an ice-warning device
and is therefore unsuitable for that purpose.
Changes in the outside temperature are dis-
played after a short delay. Indicated temperatures just above the freez-
ing point do not guarantee that the road sur-
face is free of ice. The road may still be icy,
especially in wooded areas or on bridges. You
should pay special attention to road condi-
tions when temperatures are around the
freezing point.
For more information on driving with snow
chains, see (Y page 403).
For more information on driving with summer
tires, see (Y page 402).
Observe the notes in the "Winter operation"
section (Y page 402). Off-road driving
Important safety notes G
WARNING
If you drive on a steep incline at an angle or
turn when driving on an incline, the vehicle
could slip sideways, tip and rollover. There is a risk of an accident.
Always drive on a steep incline in the line of
fall (straight up or down) and do not turn the
vehicle. G
WARNING
If the vehicle level is high, the vehicle center of gravity is raised. This could cause the vehicleto tip over more easily on uphill or downhill
gradients. There is a risk of an accident.
Select the lowest possible vehicle level.
When driving off-road, sand, mud and water,
possibly mixed with oil, for example, could get
into the brakes. This could result in a reduced braking effect or in total brake failure and also
in increased wear and tear. The braking char- acteristics change depending on the materialingressing the brakes. Clean the brakes after
driving off-road. If you detect a reduced brak- ing effect or grinding noises, have the brake
system checked in a qualified specialist work-shop as soon as possible. Adapt your driving
style to the different braking characteristics. Driving
tips
191Driving an d parking Z