Page 84 of 400

84 Controls in detailLocking and unlocking
Checking the batteries
Press button‹ orŒ.
Battery check lamp5 comes on 
briefly to indicate that the SmartKey 
batteries are in order.Unlocking and opening the trunk lid
You can unlock and open the trunk 
separately.
A minimum height clearance of 5.71 ft 
(1.74 m) is required to open the trunk lid.
Press buttonŠ until trunk unlocks 
and begins to open.
The trunk can also be opened from its 
inside in an emergency, see “Trunk lid 
emergency release” (
page 88).
!If you can no longer lock or unlock the 
vehicle with the SmartKey, then either 
the batteries in the SmartKey are dis-
charged, the SmartKey is malfunction-
ing or the vehicle battery is drained.
Check the batteries in the 
SmartKey (
page 84) and replace 
them if necessary (
page 307).
or
Use the mechanical key to unlock 
the doors (
page 305) and the 
trunk lid (
page 306) as required.
or
Use the mechanical key to lock the 
doors (
page 306) and the trunk 
lid (
page 306) as required.
or
Have the vehicle battery and the 
battery connections checked.
If the SmartKey is malfunctioning, 
contact an authorized Mercedes-Benz 
Center.!If battery check lamp5 does not 
come on briefly during check, then the 
SmartKey batteries are discharged.
Replace the batteries (
page 307). 
You can obtain the required batteries 
at any authorized Mercedes-Benz 
Center.
iIf the batteries are checked within 
signal range of the vehicle, pressing 
the‹ orŒ button will lock or 
unlock the vehicle accordingly. !The trunk lid swings open upwards 
automatically. Always make sure there 
is sufficient overhead clearance. 
     
        
        Page 263 of 400

263 Operation
Winter driving
Winter driving
Before the onset of winter, have your 
vehicle winterized at an authorized 
Mercedes-Benz Center. This service 
includes:
Check of anticorrosion and antifreeze 
concentration.
Addition of cleaning concentrate to the 
water of the windshield and headlamp 
cleaning system. Add MB Concentrate 
“S” to a premixed windshield washer 
solvent/antifreeze which is formulated 
for below freezing temperatures 
(page 358).
Battery test. Battery capacity drops 
with decreasing ambient temperature. 
A well charged battery helps to ensure 
that the engine can be started, even at 
low ambient temperatures.
Tire change. Mercedes-Benz recom-
mends M+S rated radial-ply tires with a 
minimum tread depth of approximately 1/6in (4 mm) on all four wheels for the 
winter season.
Winter tires
Always use winter tires at temperatures 
below 45°F (7°C) and whenever wintry 
road conditions prevail. Use of winter tires 
is the only way to achieve the maximum 
effectiveness of the ABS, ESP and 4MATIC 
in winter operation.
For safe handling, ensure that all mounted 
winter tires are of the same make and have 
the same tread design.Always observe the speed rating of the 
winter tires installed on your vehicle. If the 
maximum speed for which your tires are 
rated is below the speed rating of your 
vehicle, you must place a notice to this 
effect where it will be seen by the driver. 
Such notices are available from your tire 
dealer or from any authorized 
Mercedes-Benz Center.Warning!
G
Winter tires with a tread depth under 
1/6in 
(4 mm) must be replaced. They are no 
longer suitable for winter operation.
Warning!
G
If you use your spare tire when winter tires 
are fitted on the other wheels, be aware that 
the difference in tire characteristics may 
very well impair turning stability and that 
overall driving stability may be reduced. 
Adapt your driving style accordingly.
Have the spare tire replaced with a winter 
tire at the nearest authorized 
Mercedes-Benz Center. 
     
        
        Page 274 of 400

274 Practical hintsWhat to do if …
What to do if …Lamps in instrument clusterGeneral information:
If a bulb in the instrument cluster fails to 
come on during the bulb self-check when turning the SmartKey in the starter switch 
to position2, have it checked and replaced 
if necessary.Problem
Possible cause
Suggested solution
-
The yellow ABS malfunction 
indicator lamp comes on while 
driving.
The ABS has detected a malfunction and has 
switched off. The BAS and the ESP are also 
switched off (see messages in display).
The brake system is still functioning normally 
but without the ABS available.
Continue driving with added caution. 
Wheels may lock during hard braking, 
reducing steering capability. 
Have the system checked at an autho-
rized Mercedes-Benz Center as soon 
as possible.
Failure to follow these instructions 
increases the risk of an accident.
Read and observe messages in the 
display (
page 280).
The charging voltage has fallen below ten 
volts. The ABS has switched off.
When the voltage is above this value 
again, the ABS is operational again.
If necessary, have the generator 
(alternator) and battery checked. 
     
        
        Page 307 of 400

307 Practical hints
Unlocking/locking in an emergency
Changing batteries in the SmartKey
If the batteries in the SmartKey are 
discharged, the vehicle can no longer be 
locked or unlocked. It is recommended to 
have the batteries replaced 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.1Mechanical key
2Battery compartment
Replacement batteries: Lithium, type 
CR 2025 or equivalent.
Remove mechanical key1 
(page 305).
Insert mechanical key1 in side 
opening and push grey slide.
Battery compartment2 is unlatched.
Pull battery compartment2 out of the 
SmartKey housing in direction of 
arrow.
3Battery
4Contact spring
Remove the batteries.
Using a lint-free cloth, insert new 
batteries under contact spring with the 
plus (+) side facing up. 
Return battery compartment2 into 
housing until it locks into place.
Warning!
G
Keep the batteries out of reach of children.
If a battery is swallowed, seek medical help 
immediately.
iWhen changing batteries, always 
replace both batteries.
The required replacement batteries are 
available at any Mercedes-Benz 
Center.