Turning the key to MAR the warning light on the dial turns on, but it should go off as soon as the engine is started.
If the 
warning light turns on when
the car is travelling (on certain versions together with the message on the display),
stop the engine immediately and contact a Fiat Dealership.
See also:
Driver And Passenger Advanced Front Air BagInflator Units
The Driver and Passenger Advanced Front Air Bag Inflator Units are located in
the center of the steering wheel and on the right side of the instrument panel.
When the ORC detects a collision requir ...
Front and side airbags
The vehicle can be fitted with front air bags for the driver and passenger and
with side bags. ...
Pretensioners
The Fiat Doblò (with passenger's air bag ) is fitted with pretensioners on the
front side seats to improve the protection provided by the seat belts.
These devices “feel”, that a violent ...