2014 MERCEDES-BENZ B-CLASS HATCHBACK ECU

Display messages
Possible causes/consequences and
M
MSolutions Front-passenger
Front-passenger
airbag disabled airbag disabled
See Owner's Manual See 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 acci-
dent.
This poses an increased risk of injury. X Pull over and stop the vehicle safely as soon as possible, paying
attention to road and traffic conditions.
X Secure the vehicle against rolling away (Y page 181).
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 AIRBAG indicator lamps in the centre
console and the multifunction display and check the following:
Seat unoccupied and ignition switched on:
R the PASSENGER AIR BAG OFF and PASSENGER AIR BAG ON
indicator lamps must light up simultaneously for approx-
imately six seconds
R the PASSENGER AIRBAG OFF indicator lamp must then light
up and remain lit. If the indicator lamp is on, the automatic
front-passenger front airbag deactivation system has disa-
bled the front-passenger front airbag (Y page 50)
R the Front-passenger airbag enabled See Owner's Front-passenger airbag enabled See Owner's
Manual
Manual orFront-passenger
Front-passenger airbag
airbagdisabled
disabled See
SeeOwn‐
Own‐
er's Manual
er's Manual display messages must not be shown in the
multifunction display.
X Wait for a period of at least 60 seconds until the necessary sys-
tem checks have been completed.
X Make sure that the display messages do not appear in the mul-
tifunction display.
If these conditions are met, the front-passenger seat can be occu-
pied again. Whether the PASSENGER AIRBAG OFF or ON indicator
lamp remains lit or goes out depends on how the automatic front- Display
messages
263On-board computer and displays Z

Display messages
Possible causes/consequences and
M
MSolutions passenger front airbag deactivation system classifies the occu-
pant.
If the conditions are not met, the system is not operating correctly.
X Visit a qualified specialist workshop immediately.
Further information on the automatic front-passenger front airbag deactivation feature (Y page 49).Front-passenger Front-passenger
airbag airbag
enabled
enabled See
See
Owner's Manual
Owner's Manual The front-passenger front airbag is enabled during the journey
although:
R a child, a small adult or an object weighing less than the system
weight threshold is located on the front-passenger seat
or
R the front-passenger seat is not occupied
The system may detect objects or forces that are adding to the
weight applied to the seat.
G WARNING
The airbag may deploy unintentionally.
This poses an increased risk of injury. X Pull over and stop the vehicle safely as soon as possible, paying
attention to road and traffic conditions.
X Secure the vehicle against rolling away (Y page 181).
X Switch the ignition off.
X Open the front-passenger door.
X Remove the child and the child restraint system from the front-
passenger seat.
X Make sure there are no objects applying additional force to the
seat.
The system may otherwise detect the additional force and inter- pret the seat occupant's weight as greater than it actually is.
X Make sure that the seat is unoccupied, close the front-
passenger door and switch on the ignition.
X Observe the PASSENGER AIRBAG indicator lamps in the centre
console and the multifunction display and check the following:
Seat unoccupied and ignition switched on:
R the PASSENGER AIR BAG OFF and PASSENGER AIR BAG ON
indicator lamps must light up simultaneously for approx-
imately six seconds
R the PASSENGER AIRBAG OFF indicator lamp must then light
up and remain lit. If the indicator lamp is on, the automatic 264
Display
messagesOn-board computer and displays

Display messages
Possible causes/consequences and
M
MSolutions b
Rear fog lamp
Rear fog lamp The rear foglamp is faulty.
X Tail lamps (vehicles with halogen headlamps): replace the
bulb (Y page 128).
X Tail lamps (vehicles with LED headlamps): visit a qualified
specialist workshop. b
Front Front
left
leftparking
parking
lamp
lamp orFront
Front
right parking lamp
right parking lamp The front left or front right parking lamp is faulty.
X Visit a qualified specialist workshop. b
Reversing light Reversing light The reversing lamp is faulty.
X Tail lamps (vehicles with halogen headlamps): replace the
bulb (Y page 128).
X Tail lamps (vehicles with LED headlamps): visit a qualified
specialist workshop. b
Left tail lamp Left tail lamp
or
Right tail lamp
Right tail lamp The left or right-hand tail lamp is faulty.
X Visit a qualified specialist workshop. b
Left daytime driv‐ Left daytime driv‐
ing lamp ing lamp
orRight
Right
daytime driving
daytime driving
lamp lamp The left or right-hand daytime driving lamp is faulty.
X Visit a qualified specialist workshop. b
Malfunction See Malfunction See
Owner's Manual Owner's Manual The exterior lighting is faulty.
X Visit a qualified specialist workshop. Vehicles with trailer tow hitch: a fuse may have blown.
X Pull over and stop the vehicle safely as soon as possible, paying
attention to road and traffic conditions.
X Secure the vehicle against rolling away (Y page 181).
X Check the fuses (Y page 349).
X If necessary, replace the blown fuse. Observe the warning notes
as you do so.
If the display message continues to be displayed: X Visit a qualified specialist workshop. Display
messages
267On-board computer and displays Z

Display messages
Possible causes/consequences and
M
MSolutions ?
Coolant Stop vehi‐ Coolant Stop vehi‐
cle Switch engine cle Switch engine
off off The coolant is too hot.
A warning tone also sounds.
G WARNING
Never drive with an overheated engine. Driving when your engine is overheated can cause some fluids which may have leaked into
the engine compartment to catch fire.
In addition, steam from an overheated engine can cause serious
burns, which can occur just by opening the bonnet.
There is a risk of injury.
X Stop the vehicle immediately, paying attention to road and traf-
fic conditions, and switch off the engine.
X Secure the vehicle against rolling away (Y page 181).
X Wait until the engine has cooled down.
X Make sure that the air supply to the engine radiator is not
blocked, e.g. by frozen slush.
X Do not start the engine again until the display message goes out
and the coolant temperature is below 120 †. The engine may
otherwise be damaged.
X Pay attention to the coolant temperature display.
X If the temperature increases again, visit a qualified specialist
workshop immediately.
Under normal operating conditions and with the specified coolant level, the coolant temperature may rise to 120 †. #
See Owner's Manual See Owner's Manual The battery is not being charged.
A warning tone also sounds.
Possible causes:
R faulty alternator
R torn poly-V-belt
R a malfunction in the electronics
! Do not continue driving. The engine could otherwise overheat.
X Stop the vehicle immediately, paying attention to road and traf-
fic conditions, and switch off the engine.
X Secure the vehicle against rolling away (Y page 181).
X Consult a qualified specialist workshop. Display
messages
269On-board computer and displays Z

Display messages
Possible causes/consequences and
M
MSolutions #
Stop vehicle See Stop vehicle See
Owner's Manual Owner's Manual The battery is no longer being charged and the battery charge level
is too low.
A warning tone also sounds.
X Stop the vehicle immediately, paying attention to road and traf-
fic conditions, and switch off the engine.
X Secure the vehicle against rolling away (Y page 181).
X Observe the instructions in the #See Owner's Manual
See Owner's Manual
display message.
X Consult a qualified specialist workshop. 4
Check eng. oil Check eng. oil
lev. when next lev. when next
refuelling refuelling The engine oil level has dropped to the minimum level.
A warning tone also sounds.
! Avoid long journeys when there is too little coolant in the cool-
ing system. Otherwise the engine will be damaged.
X Check the oil level when next refuelling, at the latest
(Y page 320).
X If necessary, top up the engine oil (Y page 321).
X Have the engine checked at a qualified specialist workshop if the
engine oil needs topping up more often than usual.
Information on approved engine oils can be obtained from any
qualified specialist workshop or on the Internet at http://
bevo.mercedes-benz.co m.4
Add Add
1
1litre
litre engine
engine
oil
oil when
when next
next refu‐
refu‐
elling
elling The engine oil level has dropped to the minimum level.
! Avoid long journeys when there is too little coolant in the cool-
ing system. Otherwise the engine will be damaged.
X Check the oil level when next refuelling, at the latest
(Y page 320).
X If necessary, top up the engine oil (Y page 321).
X Have the engine checked at a qualified specialist workshop if the
engine oil needs topping up more often than usual.
Information on approved engine oils can be obtained from any
qualified specialist workshop or on the Internet at http://
bevo.mercedes-benz.com. 4
Engine oil level Engine oil level
Stop vehicle Stop vehicle
Switch engine off Switch engine off The engine oil level is too low. There is a risk of engine damage.
X Stop the vehicle immediately, paying attention to road and traf-
fic conditions, and switch off the engine.
X Secure the vehicle against rolling away (Y page 181).
X Check the engine oil level (Y page 320).
X If necessary, top up the engine oil (Y page 321).270
Display messagesOn-board computer and displays

Display messages
Possible causes/consequences and
M
MSolutions Lane Keeping
Lane Keeping
Assist currently Assist currently
unavailable See unavailable See
Owner's Manual Owner's Manual Lane Keeping Assist is deactivated and temporarily inoperative.
Possible causes:
R the windscreen is dirty in the camera's field of vision
R visibility is impaired due to heavy rain, snow or fog
R there have been no lane markings for an extended period
R the lane markings are worn, dark or covered, e.g. by dirt or snow
Once the causes listed above no longer apply, the display message
goes out.
Lane Keeping Assist is operational again.
If the display message does not disappear:
X Pull over and stop the vehicle safely as soon as possible, paying
attention to road and traffic conditions.
X Secure the vehicle to prevent it from rolling away (Y page 181).
X Clean the windscreen. Lane Keeping Lane Keeping
Assist inoperative Assist inoperative Lane Keeping Assist is faulty.
X Visit a qualified specialist workshop. Blind Spot Assist
Blind Spot Assist
currently unavail‐ currently unavail‐
able See Owner's able See Owner's
Manual Manual Blind Spot Assist 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 sta-
tions or other sources of electromagnetic radiation
R the radar sensor system is outside the operating temperature
range
The yellow 9indicator lamps also light up in the exterior mir-
rors.
Once the causes listed above no longer apply, the display message goes out.
Blind Spot Assist is operational again.
If the display message does not disappear:
X Pull over and stop the vehicle safely as soon as possible, paying
attention to road and traffic conditions.
X Secure the vehicle against rolling away (Y page 181).
X Restart the engine. 272
Display
messagesOn-board computer and displays

Display messages
Possible causes/consequences and
M
MSolutions Traffic Sign
Traffic Sign
Assist currently Assist currently
unavailable See unavailable See
Owner's Manual Owner's Manual Traffic Sign Assist is temporarily inoperative.
Possible causes:
R the windscreen is dirty in the camera's field of vision
R visibility is impaired due to heavy rain, snow or fog
X Clean the windscreen.
If the system detects that the camera is fully operational, the dis-
play message disappears.
Traffic Sign Assist is operational again. Traffic Sign Traffic Sign
Assist inoperative Assist inoperative Traffic Sign Assist is faulty.
X Visit a qualified specialist workshop. DISTRONIC PLUS off
DISTRONIC PLUS off DISTRONIC PLUS has been deactivated (Y
page 193).
If it was not deactivated by the driver, a warning tone also sounds. DISTRONIC PLUS
DISTRONIC PLUS
available again available again DISTRONIC PLUS is operational again after having been tempo-
rarily unavailable. You can now reactivate DISTRONIC PLUS
(Y
page 193). DISTRONIC DISTRONIC
PLUS
PLUScur‐
cur‐
rently
rently unavailable
unavailable
See Owner's Manual
See Owner's Manual DISTRONIC 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 sta-
tions or other sources of electromagnetic radiation
R the system is outside the operating temperature range
R the on-board voltage is too low
A warning tone also sounds.
Once the causes listed above no longer apply, the display message
goes out.
DISTRONIC PLUS is operational again.
If the display message does not disappear:
X Pull over and stop the vehicle safely as soon as possible, paying
attention to road and traffic conditions.
X Secure the vehicle against rolling away (Y page 181).
X Restart the engine. DISTRONIC PLUS DISTRONIC PLUS
inoperative inoperative DISTRONIC PLUS is faulty. Adaptive Brake Assist may also have
failed.
A warning tone also sounds.
X Visit a qualified specialist workshop. 274
Display
messagesOn-board computer and displays

Tyres
Display messages
Possible causes/consequences and
M
MSolutions Tyre pressure
Tyre pressure
Check tyre(s) Check tyre(s) The tyre pressure loss warning system has detected a significant
loss in pressure.
A warning tone also sounds.
Possible causes:
R you have changed the positions of the wheels and tyres or fitted
new wheels and tyres
R the tyre pressure in one or more tyres is not correct
G WARNING
Underinflated tyres pose the following risks:
R the tyres may burst, especially as the load and vehicle speed
increase
R the tyres may wear excessively and/or unevenly, which may
greatly impair tyre traction
R the driving characteristics, as well as steering and braking, may
be greatly impaired
There is a risk of an accident.
X Stop the vehicle without making any sudden steering or braking
manoeuvres. Pay attention to the traffic conditions as you do so.
X Secure the vehicle to prevent it from rolling away (Y page 181).
X Check the tyres and, if necessary, follow the instructions for a
flat tyre (Y page 334).
X Check the tyre pressures and, if necessary, correct the tyre
pressure.
X Restart the tyre pressure loss warning system when the tyre
pressure is correct (Y page 358).Check tyre pres‐ Check tyre pres‐
sures sures
then
thenrestart
restart
Run Flat Indicator
Run Flat Indicator The tyre pressure loss warning system generated a display mes-
sage and has not been restarted since.
X Set the correct tyre pressure in all four tyres.
X Restart the tyre pressure loss warning system (Y page 358).Run Run
Flat
Flat Indicator
Indicator
inoperative
inoperative The tyre pressure loss warning system is faulty.
X Visit a qualified specialist workshop. Please correct
Please correct
tyre pressure tyre pressure The tyre pressure is too low in at least one of the tyres, or the tyre
pressure difference between the wheels is too great.
X Check the tyre pressures at the next opportunity (Y page 358).
X If necessary, correct the tyre pressure.
X Restart the tyre pressure monitor (Y page 360).276
Display
messagesOn-board computer and displays