Mercedes-Benz 2008 M-Class Operator's Manual page 407

Practical hints
What to do if ...
Problem
<
The red seat belt telltale comes
on for a maximum of 6 seconds
after starting the engine.
<
You hear a warning chime for a
maximum of 6 seconds after
starting the engine.
<
The red seat belt telltale comes
on while the vehicle is standing
still and the engine is running or
during driving.
406
Possible cause/consequence
The seat belt telltale reminds you and your
passengers to fasten your seat belts before
driving off.
You have forgotten to fasten your seat belt.
You and/or your front passenger have
forgotten to fasten your seat belts.
There are items placed on the front passen-
ger seat and therefore the system senses the
front passenger seat as being occupied.
Suggested solution
Fasten your seat belts.
Regardless of whether the seat belts
are fastened or not, the seat belt tell-
tale always comes on and remains lit
for 6 seconds after starting the
engine.
Fasten your seat belt.
The warning chime stops sounding.
Fasten your seat belts.
The seat belt telltale goes out.
Remove the items from the front pas-
senger seat and put them in a safe
place.
The seat belt telltale goes out.