We investigate the high electric field dynamics of conduction electrons in dilute nitride GaAs1−xNx diodes. At low temperature (T<40K), we show that the trapping of hot electrons at localized states leads to low frequency oscillations (<1Hz) of the current at high bias. This slow dynamics is replaced at higher temperatures by a fast response of the current in the subterahertz frequency range, which we relate to the interaction of hot electrons with resonant nitrogen-related states in the conduction band.