Maybe this procedure would work. It is for a Grande Punto of 2005 but will probably work for your car too. Let us know.
Instructions
1 Turn the ignition switch to the "On" position without starting the engine.
2 Press the odometer reset button repeatedly until the total mileage is displayed.
3 Turn the ignition switch to "Off."
4 Press and hold the trip odometer reset button.
5 Turn the ignition switch to "On." Do not start the engine.
6 Release the trip odometer reset button after the service display counts down from 10 to 0 and the service light resets.
http://www.ehow.co.uk/how_7793184_reset-light-fiat-grande-punto.html
ChicksFan, April 2015