A method making it possible to diagnose whether an open load or a load is indeed present in a system including a resistive or inductive load controlled by a control transistor. The method envisages measuring the intensity of the current in the branch formed by the closed control transistor and the load, then, successively, comparing it with a positive threshold, comparing it with a negative threshold and lastly comparing its positive or negative variation over a timeframe Δt with respect to a reference slope to determine whether a load is indeed present or else an open-load situation is present. The present invention is in particular intended for use in the automotive field, to allow the reliable diagnosis of the presence or absence of an open-load situation.