Starting procedure with the SmartKey
To start the engine using the SmartKey instead of KEYLESS-GO, pull the Start/ Stop button out of the ignition lock.
•► To start a gasoline engine: turn the SmartKey to position 3 in the ignition lock and release it as soon as the engine is running.
•► To start a diesel engine: turn the SmartKey to position 2 in the ignition lock.
http://strategic-human-resource.com/The 
preglow indicator lamp in the
instrument cluster lights up.
•► When the 
preglow indicator lamp
goes out, turn the SmartKey to position 3 and release it as soon as the
engine is running.
You can start the engine without preglow if the engine is warm.
See also:
GTW (Gross Trailer Weight)
The GTW is the weight of a trailer including
the weight of the load, luggage, accessories
etc. on the trailer. ...
Important notes
In order to prevent the vehicle's battery from
discharging, the interior lighting functions are
automatically deactivated after some time
except for when the SmartKey is in position
2 in the i ...
Setting the rear-compartment airflow
using the front control panel
Turn the SmartKey to position 2 in the
ignition lock.
Activate the rear compartment
function via COMAND.
The rear-compartment climate control can
be controlled via the front control panel
...