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 BabySmartâ„¢ 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 BabySmartâ„¢ 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.