ECU MERCEDES-BENZ GLS 2017 Owner's Guide

driving characteristics and the trailer can
come loose. There is a risk of an accident.
You should only ever install a ball coupling
that has the permissible dimensions and that
is designed to meet your trailer-towing
requirements. Do not modify the ball coupling
or the trailer tow hitch.
You will find the values approved by the manu-
facturer on the vehicle identification plates and
those for the towing vehicle under "Technical
data" ( Y
page 387).
G WARNING
If the ball coupling is not installed correctly or
not secured with the bolt provided and the
corresponding spring cotter, the trailer may
come loose. There is a risk of an accident.
Always install and secure the ball coupling as
described. Before every journey, ensure that
the ball coupling is secured with the bolt and
the corresponding spring cotter.
G WARNING
When the vehicle/trailer combination begins
to lurch, you could lose control of it. The vehi-
cle/trailer combination could even rollover.
There is a risk of an accident.
On no account should you attempt to
straighten up the vehicle/trailer combination
by increasing the speed. Reduce vehicle
speed and do not countersteer. Apply the
brake as necessary.
Please observe the manufacturer's operating
instructions for the trailer coupling if a detach-
able trailer coupling is used.
Couple and uncouple the trailer carefully. If you
do not couple the trailer to the towing vehicle
correctly, the trailer could become detached.
Make sure that the following values are not
exceeded: R
the permissible trailer drawbar noseweight R
the permissible trailer load R
the permissible rear axle load of the towing
vehicle R
the maximum permissible gross vehicle
weight of both the towing vehicle and the
trailer The applicable permissible values, which must
not be exceeded, can be found: R
in the vehicle documents R
on the identification plates for the trailer tow
hitch and the trailer R
on the vehicle identification plate
If the values differ, the lowest value applies.
When towing a trailer, your vehicle's handling
characteristics will be different in comparison
with when driving without a trailer.
The vehicle/trailer combination: R
is heavier R
is restricted in its acceleration and gradient-
climbing capability R
has an increased braking distance R
is affected more by strong crosswinds R
demands more sensitive steering R
has a larger turning circle
This could impair the handling characteristics.
When towing a trailer, always adjust your speed
to the current road and weather conditions. Do
not exceed the maximum permissible speed for
your vehicle/trailer combination.
Notes on towing a trailer
General notes
! If you have a trailer tow hitch retrofitted,
changes to the cooling system and drive train
may be necessary, depending on the vehicle
type.
If you have a trailer tow hitch retrofitted,
observe the anchorage points on the chassis
frame. R
Do not exceed the legally prescribed maxi-
mum speed for vehicle/trailer combinations
in the relevant country.
This lowers the risk of an accident. R
Only install an approved trailer coupling on
your vehicle.
Further information on availability and on
installation is available from any authorized
Mercedes-Benz Center. R
The bumpers of your vehicle are not suitable
for installing detachable trailer couplings.222
Towing a trailer
Driving and parking

R
Do not install hired trailer couplings or other
detachable trailer couplings on the bumpers
of your vehicle. R
If you no longer need the ball coupling,
remove it from the ball coupling recess. This
will reduce the risk of damage to the ball cou-
pling.
When towing a trailer, set the tire pressure on
the rear axle of the towing vehicle for the max-
imum load. You will find the values in the tire
pressure table in the fuel filler flap of the vehicle
( Y
page 364).
Please note that when towing a trailer, the fol-
lowing driving systems have limited availability
or are not available at all: R
Parking Assist PARKTRONIC ( Y
page 190)R
Blind Spot Assist ( Y
page 207)R
Active Lane Keeping Assist ( Y
page 213)
On vehicles without level control, the height of
the ball coupling will alter according to the load
placed on the vehicle. If necessary, use a trailer
with a height-adjustable drawbar.
You will find installing dimensions and loads
under "Technical data" ( Y
page 387).
Driving tips Observe the information on ESP ®
trailer stabili-
zation ( Y
page 68) and on pulling away with a
trailer ( Y
page 141).
The maximum permissible speed for vehicle/
trailer combinations depends on the type of
trailer. Before beginning the journey, check the
trailer's documents to see what the maximum
permissible speed is. Observe the legally pre-
scribed maximum speed in the relevant country.
For certain Mercedes-Benz vehicles, the maxi-
mum permissible rear axle load is increased
when towing a trailer. See "Technical data" to
find out whether this applies to your vehicle
( Y
page 387). If you utilize any of the added
maximum rear axle load when towing a trailer,
the vehicle/trailer combination may not exceed
a maximum speed of 60 mph (100 km/h) for
reasons concerning the operating permit. This
also applies in countries in which the permissi-
ble maximum speed for vehicle/trailer combi-
nations is above 60 mph (100 km/h).
When towing a trailer, your vehicle's handling
characteristics will be different in comparison
with when driving without a trailer. Use the left-hand steering wheel paddle shifter
to shift into a lowe r g ear in good time on long
a
nd steep downhill gradients.
This also applies if you have activated cruise
control or Distance Pilot DISTRONIC.
This will use the braking effect of the engine, so
that less braking will be required to maintain the
speed. This relieves the load on the brake sys-
tem and prevents the brakes from overheating
and wearing too quickly. If you need additional
braking, depress the brake pedal repeatedly
rather than continuously.
Driving tips If the trailer swings from side to side: X
Do not accelerate. X
Do not counter-steer. X
Brake if necessary. R
Maintain a greater distance from the vehicle
in front than when driving without a trailer. R
Avoid braking abruptly. If possible, brake gen-
tly at first to allow the trailer to run on. Then,
increase the braking force rapidly. R
The values given for gradient-climbing capa-
bilities from a standstill refer to sea level.
When driving in mountainous areas, note that
the power output of the engine and, conse-
quently, the vehicle's gradient-climbing capa-
bility, decreases with increasing altitude.
Installing the ball coupling
G WARNING
If the ball coupling is not correctly installed
and secured, it can come loose during the
journey and endanger other road users. There
is a risk of an accident and injury.
Always install and secure the ball coupling as
described. Before every journey, ensure that
the ball coupling is secured with the bolt and
the corresponding spring cotter.
G WARNING
If the ball coupling is not installed correctly or
not secured with the bolt provided and the
corresponding spring cotter, the trailer may
come loose. There is a risk of an accident.Towing a trailer 223
Driving an d parking Z

Always install and secure the ball coupling as
described. Before every journey, ensure that
the ball coupling is secured with the bolt and
the corresponding spring cotter.
G WARNING
If the ball coupling is not installed and secured
correctly the trailer may come loose. There is
a risk of an accident.
Install and secure the ball coupling as descri-
bed in the ball coupling installation instruc-
tions. Make sure that the ball coupling is
installed and secured correctly before every
journey.
X
Pull protective cap C in the direction of the
arrow, out of the ball coupling recess. X
Stow protective cap C so that it cannot be
thrown around.
Observe the loading guidelines ( Y
page 294)
and the safety notes regarding stowage
spaces ( Y
page 294). X
Insert the ball coupling horizontally into ball
coupling recess D in the direction of the
arrow until the holes in ball coupling

X
Secure the bolt using spring cotter

Towing a trailer There are numerous legal requirements con-
cerning the towing of a trailer, e.g. speed restric-
tions. Make sure that your car/trailer combina-
tion complies with the local regulations: R
in your place of residence R
in the location to which you are driving
The police and local authorities can provide reli-
able information.
Observe the following when towing a trailer: R
To gain driving experience and to become
accustomed to the new handling characteris-
tics, you should practice the following in a
traffic-free location: -
cornering -
stopping -
backing up R
Before driving, check: -
trailer tow hitch -
safety switch for braked trailers -
safety chains -
electrical connections -
lights -
wheels R
Adjust the exterior mirrors to provide an
unobstructed view of the rear section of the
trailer. R
If the trailer has electronically controlled
brakes, pull away carefully. Brake manually
using the brake controller and check whether
the brakes function correctly. R
Secure any objects on the trailer to prevent
the cargo from slipping when the vehicle is in
motion. R
When you couple up a trailer, check at regular
intervals that the load is firmly secured. If the
tra i ler is equipped with trailer lights and
brakes, check the trailer to ensure that these
are working. R
Bear in mind that the handling will be less
stable when towing a trailer than when driving
without one. Avoid sudden steering move-
ments. R
The vehicle/trailer combination is heavier,
accelerates more slowly, has a decreased
gradient climbing capability and a longer
braking distance.
It is more susceptible to side winds and
requires more careful steering. R
If possible, do not brake suddenly, but instead
depress the brake pedal moderately at first so
that the trailer can activate its brakes. Then
increase the pressure on the brake pedal. R
If the automatic transmission repeatedly
shifts between gears on uphill or downhill gra-
dients, shift to a lower gear using the left-hand
steering wheel paddle shifter.
A lower gear and lower speed reduce the risk
of engine failure. R
When driving downhill, shift to a lower gear to
utilize the engine's braking effect.
Avoid continuous brake application as this
may overheat the vehicle brakes and, if instal-
led, the trailer brakes. R
If the coolant temperature increases dramat-
i cally while the air-conditioning system is
switched on, switch off the air-conditioning
system.
Coolant heat can also be dissipated by open-
ing the windows and switching the ventilation
blower and the interior temperature to the
highest level. R
When overtaking, pay particular attention to
the extended length of your vehicle/trailer
combination.
Due to the length of the vehicle/trailer com-
bination, you require additional road space in
relation to the vehicle you are overtaking
before you can change back to the original
lane.
Decoupling a trailer
G WARNING
If you uncouple a trailer with the overrun
brake engaged, you could trap your hand
between the vehicle and the trailer drawbar.
There is a risk of injury.
Do not uncouple a trailer if the overrun brake
is engaged.
G WARNING
Vehicles with level control:
The vehicle is lowered as soon as you discon-
nect the trailer cable. This could result in your
limbs or those of other people that are
between the vehicle body and tires or under-226
Towing a trailer
Driving an d parking

Display messages
Possible causes/consequences and P Solutions
The yellow $ warning lamp and th e red I (US A only) or $
(Canada only) indicator lamp ligh t up.
The electric parking brak e is malfunctioning .
To release: X
Switc h off th e ignition and tur n it bac k on .X
Releas e th e electric parking brak e manually.
or X
Releas e th e electric parking brak e automatically ( Y
page 160).
If th e electric parking brak e still canno t be released:X
Do no t drive on .X
Consult a qualified specialist workshop .
The red I (US A only) or $ (Canada only) indicator lamp flashes
and th e yellow $ warning lamp lights up.
The electric parking brak e is malfunctioning .
To release: X
Switc h off th e ignition and tur n it bac k on .X
Releas e th e electric parking brak e manually.
To apply : X
Switc h off th e ignition and tur n it bac k on .X
Apply th e electric parking brak e manually.
If th e red I (US A only) or $ (Canada only) indicator lamp con-
tinue s to flash: X
Do no t drive on .X
Secur e th e vehicl e against rollin g away ( Y
page 367).X
Shift th e transmission to position P .X
Turn th e fron t wheels toward s th e curb.X
Consult a qualified specialist workshop .248
Display messages
On-board computer and displays

Display messages
Possible causes/consequences and P Solutions
The yellow $ warning lamp lights up and th e red I (US A only)
or $ (Canada only) indicator lamp flashes .
It is no t possibl e to apply th e electric parking brak e manually.X
Shift th e transmission to position P .X
Visit a qualified specialist workshop .
' (USA
only)
M ( Canada
only)
Check Brake Fluid
Level There is no t enough brak e flui d in th e brak e flui d reservoir . In addition ,
th e ' (US A only) or M (Canada only) warning lamp lights up in
th e instrumen t cluste r and a warning tone sounds.
G WARNIN G
The braking effec t may be impaired.
There is a ris k of an accident.X
Pull ove r and stop th e vehicl e safely as soo n as possible, payin g
attention to roa d and traffic conditions. Do no t continu e drivin g
under any circumstances. X
Secur e th e vehicl e against rollin g away ( Y
page 159).X
Consult a qualified specialist workshop .X
Do no t add brak e fluid . This does no t correc t th e malfunction .
& Check Brake Pad Wea r The brak e pads/linings hav e reached their wear limit.
US A only: th e ' red brak e system warning lamp is lit while th e
engin e is running. X
Visit a qualified specialist workshop .
S Inoperative On e or mor e main features of th e mbrace system are malfunctioning .X
Visit a qualified specialist workshop .
Active Brake Assist
Functions Currently
Limite d See Opera‐
tor's Manual Active Brake Assis t wit h cross-traffic function is temporarily inopera-
tive.
Possibl e causes are: R
th e radar sensor system is temporarily inoperative, e.g. due to elec -
tromagneti c radiation emitted by nearby TV or radi o station s or
other source s of electromagneti c radiationR
th e system is outside th e operating temperature rangeR
th e on-boar d voltag e is to o low.
Whe n th e causes state d abov e no longer apply, th e display message
disappears.
Active Brake Assis t wit h cross-traffic function or PRE ‑ S AF E ®
PLU S is
functional again .
If th e display message does no t disappear :X
Pull ove r and stop th e vehicl e safely as soo n as possible, payin g
attention to roa d and traffic conditions.X
Secur e th e vehicl e against rollin g away ( Y
page 159).X
Restart th e engine.250
Display messages
On-board computer and displays

Display messages
Possible causes/consequences and P Solutions
Active Brake Assist
Functions Limite d
See Operator' s Man ‐
ual Active Brake Assis t is unavailable due to a malfunction . Adaptive
Brake Assis t may also hav e failed.X
Visit a qualified specialist workshop immediately.
PRE-SAFE Inopera‐
tiv e See Operator' s
Manual Importan t function s of PRE-SAF E ®
hav e failed. Al l other occupant
safet y systems , e.g. air bags , remain available.X
Visit a qualified specialist workshop immediately.
Active Brake Assist
Functions Currently
Limite d See Opera‐
tor's Manual Active Brake Assis t or PRE ‑ SAFE ®
PLU S is temporarily inoperative.
Possibl e causes are: R
function is impaire d due to heav y rain or snowR
th e radar sensor system is temporarily inoperative, e.g. due to elec -
tromagneti c radiation emitted by nearby TV or radi o station s or
other source s of electromagneti c radiationR
Mercedes-AMG vehicles: ES P ®
is deactivatedR
th e system is outside th e operating temperature rangeR
th e on-boar d voltag e is to o low.
Whe n th e causes state d abov e no longer apply, th e display message
disappears.
Active Brake Assis t or PRE ‑ SAFE ®
PLU S is operative again .
If th e display message does no t disappear :X
Pull ove r and stop th e vehicl e safely as soo n as possible, payin g
attention to roa d and traffic conditions.X
Secur e th e vehicl e against rollin g away ( Y
page 159).X
Restart th e engine.X
Mercedes-AMG vehicles: switch ES P ®
on again ( Y
page 67).
Active Brake Assist
Functions Limite d
See Operator' s Man ‐
ual Active Brake Assis t wit h cross-traffic function or PRE ‑ S AF E ®
PLU S is
no t available due to a malfunction .X
Visit a qualified specialist workshop immediately. Display messages 25 1
On-board computer and displays Z

Display messages
Possible causes/consequences and P Solutions
Radar Sensor s Dirty
See Operator' s Man ‐
ual The radar sensor system is malfunctioning .
Possibl e causes are: R
Dirt on sensor sR
Heavy rain or snow R
Whe n drivin g on inter-urban roads without traffic or infrastructure,
e.g. in desert-like area s
At least on e drivin g system or drivin g safet y system is malfunctioning
or is temporarily unavailable :R
PRE-SAF E ®
PLU SR
Active Brake Assis tR
Active Lan e Keepin g Assis tR
Active Blind Spot Assis tR
Distanc e Pilo t DISTRONI C
If th e radar sensor system in fron t is dirty, Active Blind Spot Assis t will
no t perfor m a course-correcting brak e application .
A warning tone also sounds.
Once th e caus e of th e problem is no longer present, th e drivin g and
drive safet y systems will be available again . The display message dis-
appears.
If th e display message does no t disappear :X
Pull ove r and stop th e vehicl e safely as soo n as possible, payin g
attention to roa d and traffic conditions.X
Secur e th e vehicl e against rollin g away ( Y
page 159).X
Switc h off th e engine.X
Clean all sensor s ( Y
page 328).X
Restart th e engine.
The display message disappears.
u SRS Malfunction Ser ‐
vic e Required The restrain t system is malfunctioning .
The u warning lamp also lights up in th e instrumen t cluster.
G WARNIN G
The air bags or Emergency Tensioning Devices may either be triggered
unintentionally or, in th e event of an accident, may no t be triggered .
There is an increased ris k of injury.X
Visit a qualified specialist workshop immediately.
Fo r further information about th e restrain t system, see ( Y
page 41) .
u Front Lef t Malfunc‐
tio n Servic e
Required or F ron t
Right Malfunction
Servic e Required The restrain t system has malfunctioned at th e fron t on th e lef t or right .
The u warning lamp also lights up in th e instrumen t cluster.
G WARNIN G
The air bags or Emergency Tensioning Devices may either be triggered
unintentionally or, in th e event of an accident, may no t be triggered .
There is an increased ris k of injury.X
Visit a qualified specialist workshop immediately.252
Display messages
On-board computer and displays

Display messages
Possible causes/consequences and P Solutions
Front Passenger Air ‐
bag Disabled See
Operator' s Manual The front-passenger fron t air bag is deactivated during th e journey,
eve n though : R
an adult
or R
a person of th e correspondin g statur e is on th e front-passenger seat
If additional force s are applie d to th e seat , th e system may interpret
th e occupant's weigh t as lower than it actually is.
G WARNIN G
The front-passenger air bag does no t deploy during an accident.
There is an increased ris k of injury.X
Pull ove r and stop th e vehicl e safely as soo n as possible, payin g
attention to roa d and traffic conditions.X
Secur e th e vehicl e against rollin g away ( Y
page 159).X
Switc h th e ignition off .X
Hav e th e occupant get out of th e vehicle.X
Kee p th e seat unoccupied , close th e front-passenger door and
switch on th e ignition .X
Observ e th e PASSENGER AI R BA G indicator lamp s in th e center
console and th e multifunction display and chec k th e following:
Seat unoccupied and ignition switched on :R
a self-diagnosis is carrie d out . The PASSENGER AI R BA G OF F and
PASSENGER AI R BA G ON indicator lamp s mus t ligh t up simulta-
neousl y for approximately six seconds R
th e PASSENGER AI R BA G OF F indicator lamp mus t then ligh t up
and remain lit after th e s elf-diagnosis . If th e indicator lamp is on ,
OCS (Occupant Classification System) has disabled th e front-
passenger fron t air bag ( Y
page 49 )R
th e Front Passenger Airbag Enable d See Operator' s
Manual or Front Passenger Airbag Disabled See Opera‐
tor's Manual display message s mus t no t be shown in th e mul-
tifunction display X
Wait for a period of at least 60 seconds until th e necessar y system
checks hav e been completed.X
Mak e sur e that th e display message s do no t appear in th e multi-
function display.
If these condition s are fulfilled , th e front-passenger seat can be occu-
pied again . Whether th e PASSENGER AI R BA G OF F or ON indicator
lamp remain s lit or goe s out depend s on how OCS classifies th e occu-
pant.
If th e condition s are no t fulfilled , th e system is no t operating correctly.X
Visit a qualified specialist workshop immediately.
Fo r further information about th e Occupant Classification System, see
( Y
page 49) .254
Display messages
On-board computer and displays