Mercedes-Benz 2011 E-Class Sedan Operator's Manual page 264

Display messages
262
Display messages
+
Remove 'Start'
Button and Insert
Key
+
Close Doors to
Lock Vehicle
Possible causes/consequences and M Solutions
KEYLESS-GO is temporarily malfunctioning or is defective. A
warning tone also sounds.
X
Insert the SmartKey into the ignition lock and turn it to the
desired position.
X
Visit a qualified specialist workshop.
At least one door is open. A warning tone also sounds.
X
Close all doors and lock the vehicle again.