2008 MERCEDES-BENZ C300 key battery

66 Safety and Security
Anti-theft systems
Immobilizer
The immobilizer prevents unauthorized
persons from starting your vehicle.
When leaving the vehicle, always take the
SmartKey or SmartKey with KEYLESS-GO*
(Canada only) with you and lock the
vehicle. The engine can be started by
anyone with a valid SmartKey or SmartKey
with KEYLESS-GO* (Canada only) that is
left inside the vehicle.
Activating
With the SmartKey: Remove the
SmartKey from the starter switch.
With the KEYLESS-GO* (Canada
only): Turn off the engine and open the
driver’s door.
Deactivating
Switch on the ignition.
Anti-theft alarm system
Once the alarm system has been armed, a
visual and audible alarm is triggered when
someone opens:

a door

the trunk

the hood
The alarm will stay on even if the activating
element (a door, for example) is immedi-
ately closed.
The alarm system will also be triggered
when

the vehicle is opened with the
mechanical key.

a door is opened from the inside.

the trunk is opened with the
emergency release button.
To cancel the alarm after it has been trig-
gered, see “Canceling the alarm”
(
page 67).
1Indicator lamp
iStarting the engine will also deactivate the
immobilizer.
In case the engine cannot be started (yet the
vehicle’s battery is charged), the system is not
operational. Contact an authorized
Mercedes-Benz Center or call
1-800-FOR-MERCedes (in the USA), or
1-800-387-0100 (in Canada).
iIf the alarm stays on for more than
30 seconds, a call to the Response Center is
initiated automatically by the Tele Aid* system
(
page 295) provided Tele Aid* service was
subscribed to and properly activated, and that
necessary mobile phone, power supply and GPS
coverage are available.

70 Controls in detail
Locking and unlocking
SmartKey
Your vehicle comes supplied with two
SmartKeys, each with remote control and
a removable mechanical key.
The SmartKey provides an extended oper-
ating range. To prevent theft, however, it is
advisable to only unlock the vehicle when
you are in close proximity to it.
The SmartKey centrally locks and unlocks,
when set to factory settings (
page 71):

the doors

the trunk

the fuel filler flap
SmartKey with remote control
1‹ Lock button
2ŠOpening button for trunk
(
page 269)
3Mechanical key locking tab
4ŒUnlock button
5Battery check lamp
6ÂPanic button (
page 58)
!To prevent possible malfunction, avoid ex-
posing the SmartKey to high levels of electro-
magnetic radiation.
Warning!G
When leaving the vehicle, always remove the
SmartKey from the starter switch, take it
with you, and lock the vehicle. Do not leave
children unattended in the vehicle, or with
access to an unlocked vehicle. A child’s
unsupervised access to a vehicle could
result in an accident and/or serious person-
al injury.
Warning!G
To prevent possible personal injury, always
keep hands and fingers away from the door
or trunk lid opening when closing a door or
the trunk. Be especially careful when small
children are around.
Before closing doors, make sure there is no
possibility of someone getting caught in a
door during closing.

72 Controls in detail
Locking and unlocking
The vehicle will lock again automatically
and rearm the anti-theft alarm system
within approximately 40 seconds of un-
locking if:

neither a door nor the trunk is opened

the SmartKey is not inserted in the
starter switch

the central locking/unlocking switch is
not activated
Global locking: Press button‹.
With the trunk and doors closed:

All turn signal lamps flash three
times.

An acoustic signal sounds three
times.

The locking knobs in the doors
move down.

The anti-theft alarm system is
armed.Selective setting
If you frequently travel alone, you may wish
to reprogram the SmartKey so that press-
ing buttonŒ only unlocks the driver’s
door and the fuel filler flap.
Press and hold buttonsŒ and‹
simultaneously for about 6 seconds un-
til battery check lamp5 (
page 70)
flashes twice.
The SmartKey will then function as fol-
lows:
Unlocking driver’s door and fuel fill-
er flap: Press buttonΠonce.

All turn signal lamps flash once.

An acoustic signal sounds once.

The locking knob in the driver’s
door moves up.

The anti-theft alarm system is dis-
armed.

The locator lighting will also come
on if it is dark and the feature is ac-
tivated in the control system
(
page 172).
Global unlocking: Press buttonŒ
twice.

All turn signal lamps flash once.

An acoustic signal sounds once.

The locking knobs in the doors
move up.

The anti-theft alarm system is dis-
armed.

The locator lighting will also come
on if it is dark and the feature is ac-
tivated in the control system
(
page 172).

73 Controls in detail
Locking and unlocking
Global locking: Press button‹.
With the trunk and doors closed:

All turn signal lamps flash three
times.

An acoustic signal sounds three
times.

The locking knobs in the doors
move down.

The anti-theft alarm system is
armed.
Restoring to factory setting: Press
and hold buttonsŒ and‹ si-
multaneously for about 6 seconds until
battery check lamp5 (
page 70)
flashes twice.SmartKey with KEYLESS-GO*
(Canada only)
Vehicles equipped with KEYLESS-GO come
with two SmartKeys with KEYLESS-GO,
each with remote control and a removable
mechanical key.
The KEYLESS-GO function is integrated
into the SmartKey. On these vehicles, the
validity of the SmartKey with KEYLESS-GO
is checked every time you grasp an outside
door handle.
With the KEYLESS-GO function, you can
lock and unlock the vehicle without using
the remote control buttons on the
SmartKey and start the engine without in-
serting the SmartKey in the starter switch.
The SmartKey with KEYLESS-GO centrally
locks and unlocks, when set to factory set-
tings (
page 76):

the doors

the trunk

the fuel filler flap
SmartKey with KEYLESS-GO
1‹ Lock button
2ŠOpening button for trunk
(
page 269)
3Locking tab for mechanical key
4ΠUnlock button
5Battery check lamp
6ÂPanic button (
page 58)
iWhen any outside door handle other than
the driver’s outside door handle is grasped, the
vehicle is always centrally unlocked.
!To prevent possible malfunction, avoid ex-
posing the SmartKey with KEYLESS-GO to high
levels of electromagnetic radiation.

77 Controls in detail
Locking and unlocking
Global unlocking: Grasp an outside
door handle1.

All turn signal lamps flash once.

An acoustic signal sounds once.

The locking knobs in the doors
move up.

The anti-theft alarm system is dis-
armed.

The locator lighting will also come
on if it is dark and the feature is ac-
tivated in the control system
(
page 172).
The vehicle will lock again automatically
and rearm the anti-theft alarm system
within approximately 40 seconds of un-
locking if:

neither a door nor the trunk is opened

the central locking/unlocking switch is
not activated
Global locking: Close all doors and
touch outside of door handle1. Do
not keep your hand in the door handle
recess.
With the trunk and doors closed:

All turn signal lamps flash three
times.

An acoustic signal sounds three
times.

The locking knobs in the doors
move down.

The anti-theft alarm system is
armed.Selective setting
If you frequently travel alone, you may wish
to reprogram the SmartKey with
KEYLESS-GO so when you, grasp the driv-
er’s outside door handle only the driver’s
door and the fuel filler flap unlocks.
Press and hold buttonsŒ and‹
simultaneously for about 6 seconds un-
til battery check lamp5 (
page 73)
flashes twice.
The SmartKey with KEYLESS-GO will
then function as follows:
Unlocking driver’s door and fuel fill-
er flap: Grasp the driver’s outside door
handle.

All turn signal lamps flash once.

An acoustic signal sounds once.

The locking knob in the driver’s
door moves up.

The anti-theft alarm system is dis-
armed.
iThe vehicle could inadvertently be unlocked
if the SmartKey with KEYLESS-GO is within 3 ft
(1 m) of the vehicle and:

an outside door handle is splashed with wa-
ter, or

you attempt to clean an outside door handle.
iYou can also lock the vehicle using the
KEYLESS-GO lock button on trunk lid, if equipped
(
page 270).

78 Controls in detail
Locking and unlocking

The locator lighting will also come
on if it is dark and the feature is ac-
tivated in the control system
(
page 172).
Global unlocking: Grasp any outside
door handle other than the driver’s out-
side door handle.

All turn signal lamps flash once.

An acoustic signal sounds once.

The locking knobs in the doors
move up.

The anti-theft alarm system is dis-
armed.

The locator lighting will also come
on if it is dark and the feature is ac-
tivated in the control system
(
page 172).
Global locking: Close all doors and
touch outside of a door handle1
(
page 76). Do not keep your hand in
the door handle recess.
With the trunk and doors closed:

All turn signal lamps flash three
times.

An acoustic signal sounds three
times.

The locking knobs in the doors
move down.

The anti-theft alarm system is
armed.
Restoring to factory setting: Press
and hold buttonsŒ and‹ si-
multaneously for about 6 seconds until
battery check lamp5 (
page 73)
flashes twice.Checking batteries in the SmartKey or
SmartKey with KEYLESS-GO*
(Canada only)
Press button‹ orŒ.
The battery check lamp (
page 70) or
(
page 73) comes on briefly to indi-
cate that the SmartKey or SmartKey
with KEYLESS-GO batteries are in or-
der.
iYou can also lock the vehicle using the
KEYLESS-GO lock button on trunk lid, if equipped
(
page 270).!If the battery check lamp does not come on
briefly during check, the SmartKey or SmartKey
with KEYLESS-GO batteries are discharged.
Replace the batteries (
page 428).
You can obtain the required batteries at any
authorized Mercedes-Benz Center.
iIf the batteries are checked within signal
range of the vehicle, pressing button‹ or
Πwill lock or unlock the vehicle accordingly.


82 Controls in detail
Starter switch positions
SmartKey
Starter switch
0For removing SmartKey1Power supply for some electrical con-
sumers, such as seat adjustment
2Ignition (power supply for all electrical
consumers) and driving position.
All lamps (except high beam headlamp
indicator lamp and turn signal indicator
lamps unless activated) in the instru-
ment cluster come on. If a lamp in the
instrument cluster fails to come on
when the ignition is switched on, have
it checked and replaced if necessary.
If a lamp in the instrument cluster re-
mains on after starting the engine or
comes on while driving, refer to “Lamps
in instrument cluster” (
page 374).
3Starting position
For information on starting the engine us-
ing the SmartKey, see “Starting: Make sure
the gear selector lever is set to P.”
(
page 127).
Warning!G
When leaving the vehicle, always remove the
SmartKey or SmartKey with KEYLESS-GO*
from the starter switch, take it with you, and
lock the vehicle. Do not leave children unat-
tended in the vehicle, or with access to an
unlocked vehicle. A child’s unsupervised ac-
cess to a vehicle could result in an accident
and/or serious personal injury.
iWhen you switch on the ignition, the
indicator and warning lamps (except high beam
headlamp indicator lamp and turn signal indica-
tor lamps unless activated) in the instrument
cluster come on. The indicator and warning
lamps (except high beam headlamp indicator
lamp and turn signal indicator lamps if activated)
should go out when the engine is running. This in-
dicates that the respective systems are opera-
tional.
iVehicles with automatic transmission*: The
SmartKey can only be removed from the starter
switch with the gear selector lever in positionP.
iIf the SmartKey is left in starter switch
position0 for an extended period of time, it can
no longer be turned in the switch. In this case,
the steering is locked. To unlock, remove
SmartKey from starter switch and reinsert.
!If the SmartKey cannot be turned in the
starter switch, the battery may not be sufficient-
ly charged.

Check the battery and charge it if necessary
(
page 446).

Get a jump start (page 451).
To prevent accelerated battery discharge or a
completely discharged battery, always remove
the SmartKey from the starter switch when the
engine is not in operation.

108 Controls in detail
Lighting
Exterior lamp switch
Low beam headlamps
The low beam headlamps can be switched
on and off with the exterior lamp switch us-
ing the manual headlamp mode.
Switching on: Turn the exterior lamp
switch to positionB.
The green indicator lampC in the
exterior lamp switch comes on.
iIf you drive in countries where vehicles drive
on the other side of the road than the country in
which the vehicle is registered, you must have
the headlamps modified for symmetrical low
beams. Relevant information can be obtained at
your authorized Mercedes-Benz Center.1‚Standing lamps, left (turn left two
stops)
2ˆStanding lamps, right (turn left
one stop)
3MOff
Daytime running lamp mode
(
page 110)
4*Automatic headlamp mode
Daytime running lamp mode
(
page 110)
5CParking lamps (also side marker
lamps, tail lamps, license plate
lamps, instrument panel lamps)
6BLow beam headlamps or high
beam headlamps
7‡Front fog lamps
8†Rear fog lamp
iIf you hear a warning signal you have
forgotten to switch off the low beam headlamps
or the parking lamps before opening the driver’s
door.
In addition the message
Switch Off Lights
appears in the multifunction display.
Switch off the low beam headlamps or the park-
ing lamps.
If the message
Switch Off Lights or Re-
move Key
appears in the multifunction display
remove the SmartKey from the starter switch or
switch off the automatic headlamp mode.
!Failure to switch off the exterior lamps when
leaving the vehicle may result in a discharged
battery.