System self-test
The 42 indicator lamp illuminates when you:
• turn the SmartKey to position 1 or 2 in the
ignition lock
• on vehicles with KEYLESS-GO, press the
Start/Stop button once or twice
The 
indicator lamp goes out
again after approximately six seconds.
If the indicator lamp does not
illuminate or is lit continuously, the system is
malfunctioning. Have the BabySmart™
system checked at an authorized Mercedes-
Benz Center before transporting a child on
the front-passenger seat.
For further information, see "Problems with air bag deactivation system".
WARNING 
Do not place powered-on laptops, mobile
phones, electronic tags such as those used in
skipasses or similar electronic devices on the
front passenger seat. Signals from such
devices may interfere with the BabySmart™
air bag deactivation system. Such signal
interference may cause the
indicator lamp not to come on during self-test.
The + SRS indicator lamp and/or the
indicator lamp could be
continuously lit, indicating that the system is
not functioning. The front-passenger front air
bag could deploy inadvertently or fail to
deploy in an accident.
See also:
Activating/deactivating DSR
Activating
DSR can only be activated if you are driving
no faster than 20 mph (30 km/h).
Vehicle without the Off-Road Pro Engineering
package
Vehicle with the Off-Road Pro Engineering package ...
Important safety notes
WARNING
The DISTRONIC PLUS requires familiarity with
its operational characteristics. We strongly
recommend that you review the following
information carefully before operating the
system.
...
Important safety notes
If you fail to adapt your driving style, the
driving safety systems can neither reduce the
risk of accident nor override the laws of
physics. Driving safety systems are merely
aids designed to ...