On the Fiat Ducato vehicle (our Star RV Polaris 2) it has a warning light that may show when the ignition is on.
The "DEF Low Refill" light may illuminate. This means that you will need to top up the AdBlue in your vehicle.
DEF stands for "Diesel Exhaust Fluid" and its advised to top up the AdBlue as soon as possible. You can find AdBlue at most petrol stations.