Estimating a fluid mass flow injected by an injector

An embodiment of the invention provides a method of estimating a fluid mass flow injected by an injector controlled by an Electronic Control Unit managing an internal combustion engine. The injector may comprise a fuel injector or a diesel exhaust fluid injector. The method comprises the steps of - measuring an elapsed time from a starting instant, - determining an injector energizing time as a function of a requested mass of fluid value, - activating the injector for the injector energizing time for injecting the requested mass of fluid, - adding the value of the requested mass of fluid to an accumulator variable, -repeating the preceding steps until a stopping condition is verified, - reading a final value reached by the accumulator variable when the stopping condition is verified, - dividing the final value of the accumulator variable by the final value of the elapsed time to determine an estimated mass flow of fluid injected by the injector.