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:
Body and underbody warranty
Your Fiat Punto is covered by warranty against perforation due to rust of any
original element of the structure or body. For the general terms of this warranty,
refer to Warranty Booklet booklet. ...
Shift Lever Override
If a malfunction occurs and the shift lever cannot be moved out of the PARK position,
you can use the following procedure to temporarily move the shift lever: 1. Firmly
set the parking brake.
2. ...
Deactivation
Turn the ignition key to STOP.
At the following starting operation (key at MAR), the sensor will not be reactivated
even is the stalk is on (B). In this event, to activate the rain sensor, you have ...