Turning the ignition key to MAR the warning light on the dial turns on, but it should go off after few seconds.
If the warning light stays on (on certain versions together with the message on the display), you will not have steering assistance and the effort on the steering wheel will be increased, steering is however possible. Contact Fiat Dealership.
See also:
(A) Whenever You Stop To Use TIREFIT
1. Pull over to a safe location and turn on the vehicle’s Hazard Warning flashers.
2. Verify that the valve stem (on the wheel with the deflated tire) is in a position
that is near to the ground.
...
Looking after the system
During the winter, the climate control system must be turned on at least once
a month for about ten minutes. Before summer, have the system checked at a Fiat
Dealership. ...
Capacities
(❒) For use with very cold temperatures we recommend using SELENIA PERFORMER
MULTIPOWER SAE 5W-30.
...