2008 MERCEDES-BENZ C300 Key go

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).

408 Practical hints
What to do if …?
Display Possible cause/consequencePossible solution
IReplace
Key BatteryThe batteries in the SmartKey with
KEYLESS-GO* are discharged.Replace the batteries (page 428).
Key Detected
In VehicleA SmartKey with KEYLESS-GO* (Canada
only) left in the vehicle was recognized
while locking the vehicle from the outside.Take the SmartKey with KEYLESS-GO* out of
the vehicle.
Obtain
A New KeyThe SmartKey with KEYLESS-GO* (Canada
only) must be replaced.Contact an authorized Mercedes-Benz Cen-
ter as soon as possible.
Remove "Start"
Button
And Insert KeyThe KEYLESS-GO* system (Canada only) is
malfunctioning.Remove KEYLESS-GO* button (Canada only)
from the starter switch (
page 83).
Operate the vehicle with the SmartKey in the
starter switch.
IClose Doors
To Lock VehicleYou wanted to lock the vehicle but not all
doors were closed.Close doors and lock vehicle again.
Key Does Not
Belong to VehicleYou have insert an incorrect key in the start-
er switch.Remove key and insert the correct key.
Don’t Forget
Your KeyThis display appears (for a maximum of
60 seconds) if the driver’s door is opened
with the engine turned off and no SmartKey
in the starter switch.
This message is only a reminder.Take the SmartKey or SmartKey with
KEYLESS-GO* (Canada only) with you when
leaving the vehicle.

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

425 Practical hints
Unlocking/locking in an emergency
Unlocking the trunk
A minimum height clearance of 5.9 ft
(1.90 m) is required to open the trunk lid.
Insert the mechanical key2 into the
trunk lid lock until it stops.
Turn mechanical key2 all the way
counterclockwise to position 2.
The trunk opens.
Turn the mechanical key2 back and
remove it from the trunk lid lock.
Locking the vehicle
If you cannot lock the vehicle with the
SmartKey or KEYLESS-GO* (Canada only),
do the following:
Close the front passenger door, the
rear doors and the trunk.
Open the driver’s door.
Press the central locking switch on the
driver’s door (
page 81).
The locking knobs of the front passen-
ger door and the rear doors move
down.
If the vehicle battery is disconnected or
drained:
Press down the locking knobs of
the front passenger door and the
rear doors manually.
Exit the vehicle.
Close the driver’s door.
Use the mechanical key2 to lock the
vehicle from the outside via the driver's
door. Turn the mechanical key2 to
position1.
The locking knob of the driver’s door
moves down. The vehicle is locked.
Check whether the doors and the trunk
are locked.
If necessary, lock the trunk with the
mechanical key2 (
page 272).
1Unlocking in an emergency
2Mechanical key
!The trunk lid swings open upwards automat-
ically. Always make sure there is sufficient over-
head clearance.
1Locking
2Mechanical key


428 Practical hints
Replacing SmartKey batteries
If the batteries in the SmartKey/SmartKey
with KEYLESS-GO* are discharged, the ve-
hicle can no longer be locked or unlocked.
It is recommended to have the batteries re-
placed at an authorized Mercedes-Benz
Center.Batteries contain materials that can harm
the environment if disposed of improperly.
Recycling of batteries is the preferred
method of disposal. Many states require
sellers of batteries to accept old batteries
for recycling.
Replacement batteries: Lithium, type
CR 2025 or equivalent.
Remove the mechanical key from the
SmartKey (
page 424).1Mechanical key
2Battery compartment
Insert mechanical key 1 into opening.
Press mechanical key 1 in direction of
arrow.
The battery compartment is unlatched.
Pull battery compartment 2 out of the
housing.
Warning!G
Batteries contain poisonous and corrosive
substances. Therefore keep the batteries
out of reach of children.
If a battery is swallowed, seek medical help
immediately.
Warning!G
SmartKey batteries contain Perchlorate
material, which may require special handling
and regard for the environment. Check with
your local government’s disposal guidelines.
California residents, see
http://www.dtsc.ca.gov/HazardousWaste
/Perchlorate/index.cfm.
iWhen replacing batteries, make sure they
are clean and free of lint.
iWhen replacing batteries, always replace
both batteries. The required replacement batter-
ies are available at any authorized
Mercedes-Benz Center.

429 Practical hints
Replacing SmartKey batteries
3Batteries
4Contact springs
Pull out batteries3.
Using a line-free cloth, insert new bat-
teries 3 under contact springs 4 with
the positive terminal (+) side facing up.
Return battery compartment 2 into
housing until it locks into place.
Slide the mechanical key back into the
SmartKey.
Check the operation of the SmartKey
or SmartKey with KEYLESS-GO*.