Page 209 of 489

208 Controls in detail
Retractable hardtop
Unlocked status noticed when stopped
Switch on the ignition (page 40).
To lock the retractable hardtop in its 
fully closed position, press retractable 
hardtop switch forward (
page 205).
or:
To lock the retractable hardtop in its 
fully opened position, pull up on the re-
tractable hardtop switch (
page 205).Unlocked status noticed while drivingStop the vehicle in a safe location or as 
soon as it is safe to do so.
Leave the ignition switched on.
To lock the retractable hardtop in its 
fully closed position, press retractable 
hardtop switch forward (
page 205).
or:
To lock the retractable hardtop in its 
fully opened position, pull up on the re-
tractable hardtop switch (
page 205).Problems when operating the 
retractable hardtop
Several conditions may cause the retract-
able hardtop to not open, close, or lock 
properly:
The luggage cover in the trunk is not 
closed.
Close the luggage cover in the 
trunk.
The trunk lid is open.
Close the trunk lid.
The battery voltage is too low.
Start engine and let run while open-
ing/closing the retractable hard-
top.
Warning!G
Stop the vehicle in a safe location or as soon 
as it is safe to do so and lock the hardtop be-
fore continuing to drive. You could other-
wise endanger yourself and others. 
     
        
        Page 378 of 489

377 Practical hints
What to do if …
Left displayRight displayPossible cause/consequencePossible solution
# Battery/
Alternator
Stop CarThe battery is malfunctioning.
The electro-hydraulic brake system 
requires electrical energy and 
therefore has only limited opera-
tion. Considerably greater brake 
pedal force is required and the stop-
ping distance is increased.Stop the vehicle in a safe location. 
Adjust driving to be consistent with reduced 
braking responsiveness.
Contact an authorized Mercedes-Benz 
Center.
USA only:
;
Canada only:
3
Reduced
Brake Effect
Start EngineThe battery has insufficient voltage 
and cannot supply sufficient power 
to the electro-hydraulic brake sys-
tem.Start the engine.
The message disappears when sufficient 
voltage is available.
Warning!G
Inhalation of exhaust gas is hazardous to 
your health. All exhaust gas contains carbon 
monoxide (CO), and inhaling it can cause 
unconsciousness and lead to death. Do not 
run the engine in confined areas (such as a 
garage) which are not properly ventilated. 
     
        
        Page 392 of 489

391 Practical hints
What to do if …
Left displayRight displayPossible cause/consequencePossible solution
FKey
Not DetectedThe SmartKey with KEYLESS-GO* is 
not recognized while the engine is 
running because:
The SmartKey with 
KEYLESS-GO* is not in the vehi-
cle.
There is strong radio-frequency 
interference.
Stop the vehicle in a safe location or as soon 
as it is safe to do so.
Search for the SmartKey with KEYLESS-GO*.
Otherwise the vehicle cannot be centrally 
locked nor can the engine be started again af-
ter the engine is stopped.
Operate the vehicle with the SmartKey with 
KEYLESS-GO* in the starter switch.
Key
Not DetectedThe SmartKey with KEYLESS-GO* is 
not recognized when attempting to 
start the engine with the 
KEYLESS-GO start/stop button* on 
the gear selector lever because:
The SmartKey with 
KEYLESS-GO* is not in the vehi-
cle.
The battery in the SmartKey 
with KEYLESS-GO* is not insert-
ed properly or completely dis-
charged.
Change the position of the SmartKey with 
KEYLESS-GO* in the vehicle.
Make sure the batteries in the SmartKey with 
KEYLESS-GO* are properly inserted 
(
page 407) and are not discharged 
(
page 113).
Start the engine with the SmartKey with 
KEYLESS-GO* in the starter switch if 
necessary. 
     
        
        Page 432 of 489

431 Practical hints
Batteries
Charge batteries in accordance with 
the instructions of the battery charger 
manufacturer. 
Reinstall the charged batteries. Follow 
the previously described steps in re-
verse order.
Reconnecting the batteries
Turn off all electrical consumers.
Install starter battery in the designated 
location in the engine compartment.
Install consumer battery in the desig-
nated location in the trunk.
Attach supports and brackets.
Tighten support and bracket screws.
Connect positive lead 4 (page 427) 
of the consumer battery and positive 
lead 1 (
page 427) of the starter bat-
tery and fasten covers.
Connect negative lead 2 
(
page 427) of the starter battery.
Connect negative lead 5 
(
page 427) of the consumer battery.
Reinstall the trunk floor.
Close trunk luggage cover 
(
page 211).
!Always connect the batteries in the order 
described below. Otherwise the vehicle’s elec-
tronics can be damaged.
!Never invert the terminal connections!
iThe following procedures must be carried 
out following any interruption of battery power 
(e.g. due to reconnection):
Synchronize the ESP® (page 367).
Synchronize side windows (page 203).