Page 353 of 421

350 Battery
Te ch n ica l
data Instruments
and controlsOperation DrivingInstrument
cluster displayPractical hintsCar care Index
Therefore, we strongly recommend that you have the
battery charge checked frequently, and corrected if
necessary, especially if you use the vehicle less than
approximately 200 miles (300 km) per month,
mostly for short distance trips, or if it is not used for
long periods of time.
Only charge a battery with a battery charger after the
battery has been disconnected from the vehicle’s
electrical circuit.
Always disconnect the battery negative lead first and
connect last.
When removing and connecting the battery, always
make sure that all electrical consumers are off and the
electronic key is in starter switch position 0. The
battery, its filler caps, the vent tube and the opposite
plu g must always b e securely installed w hen the veh icle
is in operation.
While the engine is running the battery terminal clamps
must not be loosened or detached, otherwise the
generator and other electronic components would be
damaged.Note:
After reconnecting the battery also set the clock (see
COMAND operator’s manual) resynchronize the front
seat head restraints, the express feature of the power
windows, the sliding / pop-up roof, and the electronic
stability program (see head restraints on page 72, power
windows on page 181, and electronic stability program
on page 274).
Battery recycling
Batteries contain materials that can harm the
environment with improper disposal.
Large 12 Volt storage batteries contain lead.
Recycling of batteries is the preferred method of
disposal.
Many states require sellers of batteries to accept old
batteries for recycling.
Page 356 of 421

353 Towing the vehicle
Te ch n ica l
data Instruments
and controlsOperation DrivingInstrument
cluster displayPractical hintsCar care Index Towing the vehicleImportant!
When towing the vehicle, please, note the following:
With the automatic central locking activated and the
electronic key in starter switch position 2 (vehicles with
KEYLESS-GO: in “On” position, see page 228), the
vehicle doors lock if the left front wheel as well as the
right rear wheel are turning at vehicle speeds of
approximately 9 mph (15 km / h) or more.
To prevent the vehicle door locks from locking,
deactivate the automatic central locking. See
“VEHICLE” under “Individual settings” on page 144.
Towing of the vehicle should only be done using the
properly installed towing eye bolt. Never attach tow
cable, tow rope or tow rod to vehicle chassis, frame
or suspension parts.
Note:
The selector lever will remain locked in position “P” and
the electronic key could not be turned in the starter
switch if the battery is disconnected or discharged. See
battery on page 349 or jump starting on page 351.
Wa r n i n g !
Prior to towing the vehicle with all wheels on the
ground, make certain that the electronic key is in
starter switch position 2.If the electronic key is left in the starter switch
position 0 for an extended period of time, it can no
longer be turned in the switch. To unlock, remove
electronic key from starter switch and reinsert.
Page 358 of 421

355 Towing the vehicle
Te ch n ica l
data Instruments
and controlsOperation DrivingInstrument
cluster displayPractical hintsCar care Index We recommend that the vehicle be transported using
flat bed equipment. This method is preferable to other
types of towing.
Important!
To prevent damage during transport, do not tie down
vehicle by its chassis or suspension parts.
The vehicle may be towed with all wheels on the ground
and the selector lever in position “N” for distances up to
30 miles (50 km) and at a speed not to exceed 30 mph
(50 km / h). The electronic key must be in starter switch
position 2.
To be certain to avoid a possibility of damage to the
transmission, however, we recommend the drive shaft
be disconnected at the rear axle drive f lange for any
towing beyond a short tow to a nearby garage.
Do not tow with sling-type equipment. Towing with
sling-type equipment over bumpy roads will damage
radiator and supports.
Use wheel lift, dolly, or flat bed equipment, with
electronic key in starter switch turned to position 0.Note:
To signal turns while being towed with hazard warning
flasher in use, turn electronic key in starter switch to
position 2 and activate combination switch for left or
right turn signal in usual manner – only the selected
turn signal will operate.
Upon canceling the turn signal, the hazard warning
flasher will operate again.
Caution!
If the vehicle is towed with the front axle raised, the
engine must be shut off (electronic key in starter switch
position 0 or 1). Otherwise, the ESP will immediately be
engaged and will apply the rear wheel brakes.
Switch off the tow-away alarm (see “VEHICLE” under
“Individual settings” on page 144) as well as the ESP
(see page 274).
Wa r n i n g !
With the engine not running, there is no power
assistance for the braking and steering systems. In
this case, it is important to keep in mind that a
considerably higher degree of effort is necessary to
brake and steer the vehicle.
Page 366 of 421
363 Electronic main key
Te ch n ica l
data Instruments
and controlsOperation DrivingInstrument
cluster displayPractical hintsCar care Index Changing batteries in the electronic main key
1Transmit buttons
2Lamp for battery check and function control
Checking batteries
If one of the transmit buttons (1) is pressed, the battery
check lamp (2) lights up briefly – indicating that the
batteries are in order.
Change batteries if the battery check lamp (2) does not
light up briefly.Changing batteries
Move locking tab (3) in direction of right arrow and
remove mechanical key (4, left arrow).
P80.20-2201-26
1
2
P80.35-2029-26
4
3
Page 367 of 421
364 Electronic main key
Te ch n ica l
data Instruments
and controlsOperation DrivingInstrument
cluster displayPractical hintsCar care Index
Insert mechanical key (4) in side opening (5) to open
latch. Press briefly (do not use mechanical key as lever)
to release battery compartment.
Remove mechanical key from side opening.
Carefully remove battery compartment in direction of
arrow (6).Change batteries (7), inserting new ones under contact
spring (8) with plus (+) side facing up.
Return battery compartment into housing until locked
in place and slide mechanical key back into electronic
main key.
P80.35-2025-26
5
4
6
P80.35-2027-26
78
Page 368 of 421
365 Electronic main key
Te ch n ica l
data Instruments
and controlsOperation DrivingInstrument
cluster displayPractical hintsCar care Index Important!
Batteries contain materials that can harm the
environment if disposed of improperly. Recycling of
batteries is the preferred method of disposal. For
disposal, please follow manufacturer’s recommendation
on battery package.
Replacement Battery:
Lithium, type CR 2025 or equivalent.Synchronizing remote control
The remote control may have to be resynchronized, if
the vehicle cannot be locked or unlocked.
To synchronize insert electronic key in starter switch.
The remote control should once again be operational.
Page 369 of 421
366 KEYLESS-GO-card
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cluster displayPractical hintsCar care Index
Changing batteries in the KEYLESS-GO-cardChecking batteries
Briefly press button (1). The indicator lamp “Unlock
driver’s door” (2) or “Global Unlock” (3) should come on
red or green.
Change batteries if indicator lamps do not illuminate,
see page 367.
P80.30-2027-26
1
2
3
Page 370 of 421
367 KEYLESS-GO-card
Te ch n ica l
data Instruments
and controlsOperation DrivingInstrument
cluster displayPractical hintsCar care Index Changing batteries
Pry open cover (1) (e.g. by using a narrow blade screw
driver) and remove batteries.
Install new batteries as indicated by the “+” and “-”
markings in the KEYLESS-GO-card.Important!
Batteries contain materials that can harm the
environment if disposed of improperly. Recycling of
batteries is the preferred method of disposal. For
disposal, please follow manufacturer’s recommendation
on battery package.
Replacement batteries:
Lithium, type CR 2025 or equivalent.