Mercedes-Benz 2010 M-Class Operator's Manual page 278

Vehicle status messages in the multifunction display
276
Display messages
G
Warning!
If the 42 indicator lamp remains out even after performing the above corrective
steps, do not have any children 12 years old and under and other small individuals use the front
passenger seat until the system has been repaired.
Possible causes/consequences and M Solutions
If above conditions are met, you can occupy the front
passenger seat again. Depending on the front passenger
classification sensed by the OCS, the 42
indicator lamp will remain illuminated or go out.
If above conditions are not met, the system is not working
properly. Have the system checked at an authorized
Mercedes-Benz Center as soon as possible.