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:
Seat belts not fastened
(red)
The warning light on the dial turns on glowing steadily with vehicle stationary
and driver’s or passenger’s seat belt not fastened correctly.
The warning light will turn on flashing when, ...
Wing window
IMPORTANT
Open and close the wing window only when the vehicle is stationary.
The Fiat Doblò may fit a handy wing window on the roof on the back of the load
compartment to carry long object ...
Parking sensors (where provided)
Parking sensors are located in the rear bumper to detect and inform the driver
(through an intermittent acoustic signal) about the presence of obstacles behind
the vehicle.
ACTIVATION
Sensors wi ...