2008 MERCEDES-BENZ C300 4MATIC stop start

404 Practical hints
What to do if …?
Display Possible cause/consequencePossible solution
•Coolant Low
Stop Vehicle!
Turn Engine OffRestart the engine.
If this message disappears from the multi-
function display:
Drive immediately to the nearest autho-
rized Mercedes-Benz Center.
If this message does not disappear from the
multifunction display:
Call Roadside Assistance.
•The cooling fan for the coolant is malfunc-
tioning.Observe the coolant temperature gauge in
the instrument cluster (
page 26).
Have the fan replaced as soon as possible.

407 Practical hints
What to do if …?
Display Possible cause/consequencePossible solution
IKey Not
DetectedThe SmartKey with KEYLESS-GO* (Canada
only) is not recognized while the engine is
running because the SmartKey with
KEYLESS-GO* (Canada only) is not in the
vehicle.Stop the vehicle in a safe location or as soon
as it is safe to do.
Search for the SmartKey.
Otherwise the vehicle cannot be centrally
locked nor can the engine be started again
after the engine is stopped.
The SmartKey with KEYLESS-GO* (Canada
only) is not recognized while the engine is
running because there is strong radio-fre-
quency interference.Stop the vehicle in a safe location or as soon
as it is safe to do.
Remove KEYLESS-GO* button (Canada only)
from the starter switch (
page 83).
Operate the vehicle with the SmartKey in the
starter switch.
IKey
Not DetectedThe SmartKey with KEYLESS-GO* (Canada
only) is momentarily not recognized.Change the position of the SmartKey in the
vehicle.
If necessary, operate vehicle using SmartKey
with KEYLESS-GO* (Canada only) in starter
switch under KEYLESS-GO* button (Canada
only) (
page 83).

409 Practical hints
What to do if …?
ITake Your Key
From IgnitionYou have forgotten to remove the
SmartKey.Remove the SmartKey from the starter
switch.
.AUTO Lamp Function
InoperativeThe light sensor is malfunctioning. Daytime
driving lamps are switched on.In the instrument cluster control system, set
lamp operation to manual mode.
Switch on headlamps using the exterior lamp
switch.
Contact an authorized Mercedes-Benz Cen-
ter as soon as possible.
Check
Center Brake LampThe high mounted brake lamp is malfunc-
tioning. This message will only appear if all
light emitting diodes have stopped working.Contact an authorized Mercedes-Benz Cen-
ter as soon as possible.
Check
Left Brake LampThe left brake lamp is malfunctioning.Replace the bulb as soon as possible
(
page 436).
Check
Right Brake LampThe right brake lamp is malfunctioning.Replace the bulb as soon as possible
(
page 436).
Display Possible cause/consequencePossible solution

414 Practical hints
What to do if …?
Display Possible cause/consequencePossible solution
.Check
Left Mirror
Turn SignalThe turn signal in the left exterior rear view
mirror is malfunctioning. This message will
only appear if all light emitting diodes have
stopped working.Have the LEDs replaced as soon as possible.
Check
Right Mirror
Turn SignalThe turn signal in the right exterior rear view
mirror is malfunctioning. This message will
only appear if all light emitting diodes have
stopped working.Have the LEDs replaced as soon as possible.
Switch Off LightsYou are getting out of the vehicle and the
lights are still switched on.Switch off the headlamps (page 108).
Turn Lights Off
Or
Remove KeyThe exterior lamp switch is set to * and
you have forgotten to take out the
SmartKey. The parking lamps remain
switched on.Switch off the headlamps (page 108).
or
Remove the SmartKey from the starter
switch.

424 Practical hints
Unlocking/locking in an emergency
Unlocking the vehicle
If you cannot unlock the vehicle with the
SmartKey or KEYLESS-GO* (Canada only),
unlock the driver’s door and the trunk us-
ing the mechanical key. Removing the mechanical key
1Mechanical key locking tab
2Mechanical key
Move locking tab1 in the direction of
arrow.
Slide mechanical key2 out of the
housing.Unlocking the driver’s door
Insert mechanical key2 into the driv-
er’s door lock until it stops.
Turn mechanical key2 counterclock-
wise to position 1.
The locking knob moves up, the driver’s
door is unlocked.
Pull the door handle to open the driv-
er’s door.
iUnlocking the vehicle with the mechanical
key and opening the driver’s door or the trunk
with the mechanical key will trigger the anti-theft
alarm system (
page 66).
To cancel the alarm, insert the SmartKey or
SmartKey with KEYLESS-GO* (Canada only) in
the starter switch.
1Unlocking
2Mechanical key

448 Practical hints
Battery
Starter battery
1Battery
2Positive terminal
3Negative terminal
4Ventilation hose
Disconnecting the battery
Apply the parking brake (page 134).
Make sure gear selector lever* is set to
positionP (manual transmission to
Neutral).
Turn off all electrical consumers.
Remove SmartKey from starter switch.Vehicles with KEYLESS-GO* (Canada
only):
Press the start / stop button until
the engine shuts off.
Open the driver’s door.
Open the hood (page 325).
Remove the filter box (page 447).
Read and observe safety instructions
and precautions (
page 446).
Disconnect the battery negative lead
from negative terminal3.
Remove cover from the positive
terminal2.
Disconnect the battery positive lead.iIf the battery is discharged, you must use
the mechanical key to unlock (
page 424) or
lock (
page 425) the vehicle.
Warning!G
With a disconnected battery

you will no longer be able to turn the
SmartKey in the starter switch and
pressing the KEYLESS-GO* start/stop
button (Canada only) will have no effect

vehicles with automatic transmission*:
the gear selector lever will remain
locked in positionP
!Always disconnect the starter battery in the
order described below. You could otherwise
damage the vehicle’s electronics.

456 Practical hints
Fuses
The electrical fuses in your vehicle serve to
switch off malfunctioning power circuits.
If a fuse is blown, the component(s) and
systems secured by that fuse will stop op-
erating.If a newly inserted fuse blows again, have
the cause determined and rectified at an
authorized Mercedes-Benz Center.
A fuse chart explains the fuse allocation
and fuse amperages. It is located in the
main fuse box in the passenger compart-
ment (
page 457).
The electrical fuses are located in different
fuse boxes:

Fuse box in passenger compartment
(
page 457)

Fuse box in engine compartment
(
page 457)

Fuse box in trunk (page 458)Before replacing fuses:
Depress the parking brake
(
page 134).
Make sure the manual transmission is
in Neutral (
page 136), automatic
transmission* is set to P (
page 140).
The gear position indicator in the ta-
chometer display should be on P.
Turn off all electrical consumers.
Turn off the engine (page 134).
Remove the SmartKey from the starter
switch.
Vehicles with KEYLESS-GO*
(Canada only):
Open the driver’s door.
Warning!G
Only use fuses approved by Mercedes-Benz
with the specified amperage for the system
in question and do not attempt to repair or
bridge a blown fuse. Using other than ap-
proved fuses or using repaired or bridged
fuses may cause an overload leading to a
fire, and/or cause damage to electrical
components and/or systems. Have the
cause determined and remedied at an au-
thorized Mercedes-Benz Center.
iA blown fuse must be replaced by an appro-
priate spare fuse (recognizable by its color or the
fuse rating given on the fuse) of the amperage
recommended in the fuse chart.
Any Mercedes-Benz Center will be glad to advise
you on this subject.
!Switch off the vehicle’s internal electrical
functions (
page 448) when you are working on
the fuses.
iIn case of a blown fuse contact Roadside
Assistance or an authorized Mercedes-Benz
Center.