2016 MERCEDES-BENZ GLS SUV ECU

Problems with trailer towing
Problem
Possible causes/consequences and
M
MSolutions The displaced ball cou-
pling does not reach the
securely locked position. R
The indicator lamp in the button flashes.
R The Check trailer hitch lock Check trailer hitch lock message appears in the multi-
function display.
X Initiate a new swivelling procedure.
If the ball coupling does not reach the safely engaged position as a
result:
X Start the engine
or
X Pull and hold the button during the whole swivelling procedure.
If the unlocked ball coupling does not reach the safely engaged posi- tion even after several attempts:
X Make sure that there is sufficient ground clearance before continu-
ing the journey.
X Consult a qualified specialist workshop.
As long as the Check trailer hitch lock
Check trailer hitch lock display message is
shown in the multifunction display, no trailer should be attached. Unlocking using the
button in the tailgate:
The ball coupling does
not swivel, even though:
R
the vehicle is station-
ary
R no trailer cable is con-
nected
R the button was briefly
pulled The on-board voltage is too low.
X Start the engine.
If the ball coupling still does not unlock:
X Consult a qualified specialist workshop. Towing a trailer
239Driving and parking Z

Problem
Possible causes/consequences and
M
MSolutions Unlocking using the
button in the driver's
door:
The ball coupling does
not swivel, even though:
R the vehicle is station-
ary
R no trailer cable is con-
nected The on-board voltage is too low.
X Engage park position P.
X Switch on the power supply.
or X Start the engine.
If the ball coupling still does not unlock: X Consult a qualified specialist workshop. The ball coupling does
not swivel. The indicator
lamp in the button is
flashing permanently.
The
Check trailer Check trailer
hitch lock
hitch lock message
appears in the multifunc- tion display. There is a malfunction in the release electronics.
X When the ball coupling is retracted: pull and hold the button in
the tailgate until the ball coupling engages into a securely engaged
and locked in a vertical position and then engages again under the
bumper.
X When the ball coupling is extended: pull and hold the button in
the tailgate until the ball coupling engages underneath the bumper.
If the ball coupling still does not unlock:
X Consult a qualified specialist workshop. 240
Towing a trailerDriving and parking

Display messages
Possible causes/consequences and
M
MSolutions The yellow
!warning lamp and the red !indicator lamp are lit.
The electric parking brake is malfunctioning.
To release:
X Turn the ignition off and then back on.
X Release the electric parking brake manually.
or
X Release the electric parking brake automatically (Y page 170).
If the electric parking brake still cannot be released:
X Do not drive on.
X Consult a qualified specialist workshop. The red
!indicator lamp flashes and the yellow !warning lamp
is lit.
The electric parking brake is malfunctioning.
To release:
X Turn the ignition off and then back on.
X Release the electric parking brake manually.
To apply: X Turn the ignition off and then back on.
X Apply the electric parking brake manually.
If the red !indicator lamp continues to flash:
X Do not drive on.
X Secure the vehicle against rolling away (Y page 370).
X Shift the transmission to position P.
X Turn the front wheels towards the kerb.
X Consult a qualified specialist workshop. The yellow
!warning lamp lights up. The red !indicator lamp
flashes for about ten seconds after the electric parking brake has been applied or released. It then goes out or remains lit.
The electric parking brake is malfunctioning.
X Turn the ignition off and then back on.
X Apply the electric parking brake.
If you cannot apply the electric parking brake:
X Shift the transmission to position P.
X Consult a qualified specialist workshop.
If it is not possible to release the electric parking brake:
X Release the electric parking brake automatically (Y page 170).
If the electric parking brake still cannot be released:
X Consult a qualified specialist workshop. 262
Display
messagesOn-board computer and displays

Display messages
Possible causes/consequences and
M
MSolutions The yellow
!warning lamp lights up. If you manually apply or
release the electric parking brake, the red !indicator lamp
flashes.
The electric parking brake is malfunctioning. The electric parking
brake cannot be applied manually.
X Shift the transmission to position P.
X Consult a qualified specialist workshop. !
Parking brake inop‐ Parking brake inop‐
erative erative The yellow
!warning lamp lights up. The red !indicator lamp
flashes for about ten seconds after the electric parking brake has been applied or released. It then goes out or remains lit.
The electric parking brake is malfunctioning, e.g. because of over-
voltage or undervoltage.
X Rectify the cause of the overvoltage or undervoltage, e.g. by charg-
ing the battery or restarting the engine.
X Apply or release the electric parking brake.
If the electric parking brake still cannot be applied or released: X Turn the ignition off and then back on.
X Apply or release the electric parking brake.
If the electric parking brake still cannot be released:
X Consult a qualified specialist workshop.
If the electric parking brake still cannot be applied:
X Consult a qualified specialist workshop. The yellow
!warning lamp lights up and the red !indicator
lamp flashes.
The electric parking brake cannot be applied manually.
X Shift the transmission to position P.
X Consult a qualified specialist workshop. J
Check brake fluid Check brake fluid
level level There is insufficient brake fluid in the brake fluid reservoir. In addition,
the J warning lamp in the instrument cluster lights up and a warn-
ing tone sounds.
G WARNING
Braking efficiency may be impaired.
There is a risk of an accident.
X Stop the vehicle immediately, paying attention to road and traffic
conditions. Do not continue driving.
X Secure the vehicle against rolling away (Y page 168).
X Consult a qualified specialist workshop.
X Do not top up the brake fluid. This does not correct the fault. #
Check Check
brake
brakepad
padwear
wear The brake pads/linings have reached their wear limit.
X Consult a qualified specialist workshop. Display
messages
263On-board computer and displays Z

Display messages
Possible causes/consequences and
M
MSolutions G
Inoperative
Inoperative One or more main features of the Mercedes-Benz Contact system are
malfunctioning.
X Consult a qualified specialist workshop. Active
Active
Brake
BrakeAssist
Assist
Functions
Functions currently
currently
limited
limited See
SeeOwner's
Owner's
Manual
Manual Active Brake Assist with cross-traffic function is temporarily inopera-
tive.
Possible causes:
R The radar sensor system is temporarily inoperative, e.g. due to
electromagnetic radiation emitted by nearby TV or radio stations or
other sources of electromagnetic radiation.
R The system is outside the operating temperature range.
R The on-board voltage is too low.
Once the causes listed above no longer apply, the display message
goes out.
Active Brake Assist with cross-traffic function or PRE ‑SAFE®
PLUS is
functional again.
If the display message does not disappear:
X Stop the vehicle, paying attention to road and traffic conditions.
X Secure the vehicle against rolling away (Y page 168).
X Restart the engine. Active Active
Brake
BrakeAssist
Assist
Functions limited
Functions limited
See Owner's Manual See Owner's Manual Active Brake Assist is unavailable due to a malfunction. Adaptive
Brake Assist may also have failed.
X Consult a qualified specialist workshop immediately. PRE-SAFE inopera‐
PRE-SAFE inopera‐
tive see Owner's tive see Owner's
Manual Manual
Important functions of PRE-SAFE
®
have failed. All other occupant
safety systems, e.g. airbags, remain available.
X Consult a qualified specialist workshop immediately. 264
Display
messagesOn-board computer and displays

Display messages
Possible causes/consequences and
M
MSolutions Active
Active
Brake
BrakeAssist
Assist
Functions
Functions currently
currently
limited
limited See
SeeOwner's
Owner's
Manual
Manual Active Brake Assist or PRE‑SAFE
®
PLUS is temporarily inoperative.
Possible causes:
R The function is impaired due to heavy rain or snow.
R The radar sensor system is temporarily inoperative, e.g. due to
electromagnetic radiation emitted by nearby TV or radio stations or
other sources of electromagnetic radiation.
R Mercedes-AMG vehicles: ESP ®
is deactivated.
R The system is outside the operating temperature range.
R The on-board voltage is too low.
Once the causes listed above no longer apply, the display message
goes out.
Active Brake Assist or PRE‑SAFE ®
PLUS is operative again.
If the display message does not disappear:
X Stop the vehicle, paying attention to road and traffic conditions.
X Secure the vehicle against rolling away (Y page 168).
X Restart the engine.
X Mercedes-AMG vehicles: reactivate ESP ®
(Y page 73). Active Active
Brake
BrakeAssist
Assist
Functions limited
Functions limited
See Owner's Manual See Owner's Manual Active Brake Assist with cross-traffic function or PRE
‑SAFE®
PLUS is
not available due to a fault.
X Consult a qualified specialist workshop immediately. Display
messages
265On-board computer and displays Z

Display messages
Possible causes/consequences and
M
MSolutions Radar
Radar
sensors
sensors dirty
dirty
See Owner's Manual
See Owner's Manual The radar sensor system is malfunctioning.
Possible causes:
R Dirt on sensors
R Heavy rain or snow
R Driving on inter-urban roads without traffic or infrastructure, e.g. in
desert-like areas
At least one driving system or driving safety system is malfunctioning
or is temporarily unavailable:
R PRE-SAFE ®
PLUS
R Active Brake Assist
R Active Lane Keeping Assist
R Active Blind Spot Assist
R Distance Pilot DISTRONIC
If the radar sensor system in front is dirty, Active Blind Spot Assist will not perform a course-correcting brake application.
A warning tone also sounds.
Once the cause of the problem is no longer present, the driving and
driving safety systems will be available again. The display message
disappears.
If the display message does not disappear:
X Stop the vehicle, paying attention to road and traffic conditions.
X Secure the vehicle against rolling away (Y page 168).
X Switch off the engine.
X Clean all sensors (Y page 341).
X Restart the engine.
The display message disappears. ü Mercedes-AMG vehicles only:
If this symbol appears in the multifunction display, a seat belt tongue
has been inserted into a rear seat belt buckle.
Further information on the status indicator for the rear seat belts
(Y page 47). ý Mercedes-AMG vehicles only:
If this symbol appears in the multifunction display, a seat belt tongue
has not been inserted in a rear seat belt buckle.
G WARNING
A seat belt which is not worn correctly, or which has not been engaged
in the seat belt buckle correctly, cannot provide the intended level of protection.
This poses an increased risk of injury.
X If necessary, ask the occupants in the rear to fasten their seat belts
(Y page 46).
Further information on the status indicator for the rear seat belts
(Y page 47). 266
Display
messagesOn-board computer and displays

Display messages
Possible causes/consequences and
M
MSolutions Front-passenger
Front-passenger
airbag airbag
disabled
disabled See
See
Owner's Manual
Owner's Manual The front-passenger front airbag is disabled during the journey
although:
R an adult
or
R a person of the corresponding stature is on the front-passenger seat
If additional forces are applied to the seat, the weight the system
detects may be too low.
G WARNING
The front-passenger front airbag does not deploy during an accident.
This poses an increased risk of injury.
X Stop the vehicle immediately, paying attention to road and traffic
conditions.
X Secure the vehicle against rolling away (Y page 168).
X Switch the ignition off.
X Have the occupant on the front-passenger seat step out of the
vehicle.
X Make sure that the seat is unoccupied, close the front-passenger
door and switch on the ignition.
X Observe the PASSENGER AIR BAG indicator lamps in the centre
console and the multifunction display and check the following:
Seat unoccupied and ignition switched on:
R A self-diagnosis is carried out. The PASSENGER AIR BAG OFF and
PASSENGER AIR BAG ON indicator lamps light up simultaneously for approximately six seconds.
R The PASSENGER AIR BAG OFF indicator lamp must then light up
and remain lit after the self-diagnosis. If the indicator lamp is on,
the automatic front-passenger front airbag deactivation system
has disabled the front-passenger front airbag (Y page 50)
R The Front-passenger airbag enabled See Owner's Man‐
Front-passenger airbag enabled See Owner's Man‐
ual ual orFront-passenger airbag disabled See Owner's
Front-passenger airbag disabled See Owner's
Manual
Manual display messages must not be shown in the multifunction
display
X Wait for a period of at least 60 seconds until the necessary system
checks have been completed.
X Make sure that the display messages do not appear in the multi-
function display.
If these conditions are met, the front-passenger seat can be occupied again. Whether the PASSENGER AIR BAG OFF or ON indicator lamp
remains lit or goes out depends on how the automatic front-passenger
front airbag deactivation system classifies the occupant.
If the conditions are not met, the system is not operating correctly.
X Consult a qualified specialist workshop immediately.
Further information on the automatic front-passenger front airbag
deactivation feature (Y page 50).268
Display
messagesOn-board computer and displays