A method of monitoring a valve in a turboshaft engine, said valve switching, by closing and/or opening, in response to a control instruction sent at a determined instant, said method comprising calculating a first form of a time signal from the change in a status variable of said turboshaft engine reacting to a switching of said valve, applying a signature test of the switching of the valve to a form of said signal, wherein the method further comprises defining a time interval after sending said control instruction to perform said signature test; acquiring one or more parameters other than the switching of the valve; modelling a signal of said time signal in response to a change in said other parameter(s) to calculate its change; and calculating said second form of the signal is calculated from the first form of the signal by subtracting therefrom the change in the signal calculated from the change in said other parameter(s), over said time interval following a control instruction.