2012 MERCEDES-BENZ B-CLASS Owners Manual

Display messages Possible causes/consequences and
M Solutions$(USA
only)J(Canada
only)
Check Brake Fluid
Level There is not enough brake fluid in the brake fluid reservoir.
In addition, the $ (USA only)/J (Canada only) warning
lamp lights up in the instrument cluster and a warning tone
sounds.
G WARNING
The braking effect may be impaired.
There is a risk of an accident.
X Pull over and stop the vehicle safely as soon as possible, paying
attention to road
and traffic conditions. Do not continue driving
under any circumstances.
X Secure the vehicle against rolling away ( Y page 149).
X Consult a qualified specialist workshop.
X Do not add brake fluid. This does not correct the malfunction. #
Check Brake Pad
Wear The brake pads/linings have reached their wear limit.
X
Visit a qualified specialist workshop. G
mbrace Inoperative One or more main features of the mbrace system are
malfunctioning.
X
Have the mbrace system checked immediately at a qualified
specialist workshop. 6
SRS Malfunction
Service Required There is a malfunction in the SRS (Supplemental Restraint
System). The 6 warning lamp also lights up in the instrument
cluster.
G WARNING
The air bags or Emergency Tensioning Devices may either be
triggered unintentionally or, in the event of an accident, may not
be triggered.
There is an increased risk of injury.
X Visit a qualified specialist workshop.
Further information on occupant safety (Y page 38). Display messages
207
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Display messages Possible causes/consequences and
M Solutions6
Front Left
Malfunction
Service Required 
or Front Right
Malfunction
Service Required SRS has malfunctioned at the front on the left or right. The
6
warning lamp also lights up in the instrument cluster.
G WARNING
The air bags or Emergency Tensioning Devices may either be
triggered unintentionally or, in the event of an accident, may not
be triggered.
There is an increased risk of injury.
X Visit a qualified specialist workshop. 6
Rear Left
Malfunction
Service Required 
or Rear Right
Malfunction
Service Required SRS has malfunctioned at the rear on the left or right. The
6
warning lamp also lights up in the instrument cluster.
G WARNING
The air bags or Emergency Tensioning Devices may either be
triggered unintentionally or, in the event of an accident, may not
be triggered.
There is an increased risk of injury.
X Visit a qualified specialist workshop. 6
Rear Center
Malfunction
Service Required SRS has malfunctioned at the rear center. The
6 warning lamp
also lights up in the instrument cluster.
G WARNING
The air bags or Emergency Tensioning Devices may either be
triggered unintentionally or, in the event of an accident, may not
be triggered.
There is an increased risk of injury.
X Visit a qualified specialist workshop. 6
Left Side Curtain
Airbag
Malfunction
Service Required  
or 
Right Side
Curtain Airbag
Malfunction
Service Required There is a malfunction in the left-hand or right-hand window
curtain air bag. The
6 warning lamp also lights up in the
instrument cluster.
G WARNING
The left or right window curtain air bag may either be triggered
unintentionally or, in the event of an accident, may not be
triggered.
There is an increased risk of injury.
X Visit a qualified specialist workshop. Lights
i Display messages about LEDs:208
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This display message will only appear if all LEDs have failed.
Display messages Possible causes/consequences and
M Solutionsb
Check Left
Cornering Light
 or 
Check Right
Cornering Light The left or right-hand cornering light is defective.
X
Check whether you are permitted to replace the bulb yourself
(Y page 104).
or
X Visit a qualified specialist workshop. b
Check Left Low
Beam or Check
Right Low Beam The left or right-hand low-beam headlamp is defective.
X
Check whether you are permitted to replace the bulb yourself
(Y page 104).
or
X Visit a qualified specialist workshop. b
Check Rear Left
Turn Signal or 
Check Rear Right
Turn Signal The rear left-hand or rear right-hand turn signal is defective.
X
Check whether you are permitted to replace the bulb yourself
(Y page 104).
or
X Visit a qualified specialist workshop. b
Check Front Left
Turn Signal or 
Check Front Right
Turn Signal The front left-hand or front right-hand turn signal is defective.
X
Check whether you are permitted to replace the bulb yourself
(Y page 104).
or
X Visit a qualified specialist workshop. b
Check Left Mirror
Turn Signal or 
Check
Right
Mirror
Turn Signal The turn signal in the left-hand or right-hand exterior mirror is
defective.
X
Check whether you are permitted to replace the bulb yourself
(Y page 104).
or
X Visit a qualified specialist workshop. b
Check Center
Brake
Lamp The high-mounted brake lamp is faulty.
X
Check whether you are permitted to replace the bulb yourself
(Y page 104).
or
X Visit a qualified specialist workshop. Display messages
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Display messages Possible causes/consequences and
M Solutionsb
Check Left Brake
Lamp or Check
Right Brake Lamp The left or right-hand brake lamp is defective.
X
Check whether you are permitted to replace the bulb yourself
(Y page 104).
or
X Visit a qualified specialist workshop. b
Check Left Tail
and Brake Lamps
 or 
Check Right Tail
and Brake Lamps The left or right-hand tail lamp/brake lamp is defective.
X
Check whether you are permitted to replace the bulb yourself
(Y page 104).
or
X Visit a qualified specialist workshop. b
Check Left High
Beam or Check
Right High Beam The left or right-hand high beam is defective.
X
Check whether you are permitted to replace the bulb yourself
(Y page 104).
or
X Visit a qualified specialist workshop. b
License Plate Lamp The left or right-hand license plate lamp is defective.
X
Check whether you are permitted to replace the bulb yourself
(Y page 104).
or
X Visit a qualified specialist workshop. b
Check Left Fog
Lamp or Check
Right Fog Lamp The left-hand or right-hand front fog lamp is defective.
X
Check whether you are permitted to replace the bulb yourself
(Y page 104).
or
X Visit a qualified specialist workshop. b
Rear Fog Lamp The rear fog lamp is defective.
X
Check whether you are permitted to replace the bulb yourself
(Y page 104).
or
X Visit a qualified specialist workshop. b
Check Front Left
Parking Lamp or 
Check Front Right
Parking Lamp The front left or front right parking or standing lamp is defective.
X
Check whether you are permitted to replace the bulb yourself
(Y page 104).
or
X Visit a qualified specialist workshop.210
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Display messages Possible causes/consequences and
M Solutionsb
Backup Light The backup lamp is defective.
X
Check whether you are permitted to replace the bulb yourself
(Y page 104).
or
X Visit a qualified specialist workshop. b
Check Left Tail
Lamp or Check
Right Tail Lamp The left or right-hand tail lamp is defective.
X
Check whether you are permitted to replace the bulb yourself
(Y page 104).
or
X Visit a qualified specialist workshop. b
Check Front Left
Sidemarker Lamp
 or 
Check Front Right
Sidemarker Lamp The left or right front side marker lamp is defective.
X
Check whether you are permitted to replace the bulb yourself
(Y page 104).
or
X Visit a qualified specialist workshop. b
Check Rear Left
Sidemarker Lamp
 or 
Check Rear Right
Sidemarker Lamp The rear left or right side marker lamp is defective.
X
Check whether you are permitted to replace the bulb yourself
(Y page 104).
or
X Visit a qualified specialist workshop. b
Check Left
Daytime
Running Light
 or 
Check Right
Daytime Running
Light The left-hand or right-hand daytime running lamp is faulty.
X
Check whether you are permitted to replace the bulb yourself
(Y page 104).
or
X Visit a qualified specialist workshop. b
Active Light
System Inoperative The active light function is defective.
X
Visit a qualified specialist workshop. b
Malfunction See
Operator's Manual The exterior lighting is defective.
X
Visit a qualified specialist workshop. b
Auto Lamp Function
Inoperative The light sensor is defective.
X
Visit a qualified specialist workshop. Display messages
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Display messages Possible causes/consequences and
M Solutionsb
Switch Off Lights The lights are still switched on when you leave the vehicle. A
warning tone also sounds.
X
Turn the light switch to Ã. Adaptive Highbeam
Assist Inoperative Adaptive Highbeam Assist is faulty.
X
Visit a qualified specialist workshop. Adaptive Highbeam
Assist Currently
Unavailable See
Operator's Manual Adaptive Highbeam Assist is deactivated and temporarily
inoperative. Possible causes are:
R
the windshield in the camera's field of vision is dirty.
R visibility is impaired due to heavy rain, snow or fog.
X Clean the windshield.
If the system detects that the camera is fully operational again,
the Adaptive Highbeam Assist Now Available message is
displayed.
Adaptive Highbeam Assist is operational again. Engine
Display messages Possible causes/consequences and
M Solutions+
Check Coolant
Level See
Operator's Manual The coolant level is too low.
!
Avoid making long
journeys with too little coolant in the engine
cooling system. The engine will otherwise be damaged.
X Add coolant, observing the warning notes before doing so
(Y page 269).
X If coolant needs to be added more often than usual, have the
engine coolant system checked at a qualified specialist
workshop. ? The fan motor is faulty.
X
At coolant temperatures below 248 ‡ (120 †), drive to the
nearest qualified specialist workshop.
X Avoid subjecting the engine to heavy loads, e.g. driving in
mountainous terrain, and stop-and-go traffic.212
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Display messages Possible causes/consequences and
M Solutions?
Coolant Too Hot
Stop Vehicle Turn
Engine Off The coolant is too hot.
A warning tone also sounds.
G WARNING
Do not drive when your engine is overheated. This can cause some
fluids which may have leaked into the engine compartment to
catch fire.
Steam from the overheated engine can also cause serious burns
which can occur just by opening the hood.
There is a risk of injury.
X Pull over and stop the vehicle safely and switch off the engine,
paying attention to road and traffic conditions.
X Secure the vehicle against rolling away ( Y page 149).
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 snow, slush or ice.
X Do not start the engine again until the display message goes out
and the coolant temperature is below 248 ‡ (120 †).
Otherwise, the engine could 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 248 ‡ (120 †). # The battery is not being charged.
A warning tone also sounds.
Possible causes are:
R
a defective alternator
R a torn poly-V-belt
R a malfunction in the electronics
X Pull over and stop the vehicle safely and switch off the engine,
paying attention to road and traffic conditions.
X Open the hood.
X Check whether the poly-V-belt is torn.
If the poly-V-belt is torn:
! Do not continue

driving. The engine could otherwise overheat.
X Consult a qualified specialist workshop.
If the poly-V-belt is not damaged:
X Visit a qualified specialist workshop immediately. Display messages
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Display messages Possible causes/consequences and
M Solutions4
Check Engine Oil
At Next Refueling The engine oil level has dropped to the minimum level.
A warning tone also sounds.
X
Check the oil level when next refueling, at the latest
(Y page 267).
X If necessary, add engine oil ( Y page 268).
X Have the engine checked at a qualified specialist workshop if
engine oil needs to be added more often than usual.
! Avoid long journeys with too little engine oil. The engine will
otherwise be damaged.
Information on approved engine oils can be obtained from any
qualified specialist workshop or on the Internet at http://
bevo.mercedes-benz.com (USA only). æ
Fuel Level Low The fuel level has dropped into the reserve range.
X
Refuel at the nearest gas station. ç There is only a very small amount of fuel in the fuel tank.
X
Refuel at the nearest gas station without fail. æ
Gas Cap Loose The fuel system pressure is too low. The fuel filler cap is not closed
correctly or the fuel system is leaking.
X
Check that the fuel filler cap is correctly closed.
If the fuel filler cap is not correctly closed:
X Close the fuel filler cap.
If the fuel filler cap is correctly closed:
X Visit a qualified specialist workshop.214
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