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:
How To Engage The Automatic Locking Mode
1. Buckle the combination lap and shoulder belt.
2. Grasp the shoulder portion and pull downward until the entire belt is extracted.
3. Allow the belt to retract. As the belt retracts, you will hear ...
Initial check
Turning the ignition key to MAR, the multifunction display shows the message
“Check active”: the diagnostic phase of all the electronic systems on the car has
started. This lasts few seconds: if n ...
How to warm up the engine after it has just started (petrol and diesel versions)
Proceed as follows:
❒ Drive off slowly, letting the engine turn at medium revs. Do not accelerate
abruptly;
❒ Do not drive at full performance for the initial kilometres. Wait until ...