Resetting the tyre pressure warning light on your Fiat
Most UK Fiats from about 2015 (500, Panda, Tipo, 500X) use an indirect system called iTPMS, so you reset it after setting the pressures. Ignore US guides: American 500s have sensors.
Inflate all four tyres to the handbook pressures, cold.
Stop, with the ignition on.
500X: Main Menu > Vehicle info > Reset tyre pressure, holding OK for 2 seconds until 'Reset saved'. Tipo: hold the Reset button on the left control panel for 2 seconds.
Drive. It learns best on a straight road at about 50 mph for 20 minutes.
500 and Punto
Press MENU briefly until 'Reset' shows, choose Yes with + or –, press MENU to Confirm and choose Yes again. 'Reset saved' appears.
When to reset: Reset every time you change a pressure, replace or rotate a tyre, or fit the space-saver.
Menu names vary by model and year, so check your handbook if yours looks different. More in what the warning light means.