We propose a dynamically tunable nonreciprocal response for wave propagations by employing nonlinear Fano resonances. We demonstrate that transmission contrast of waves propagation in opposite directions can be controlled by excitation signal. In particular, the unidirectional transmission can be flipped at different times of a pulse, resembling a diode operation with {\em dynamical reconfigurable nonreciprocity}. The key mechanism is the interaction between the linear and nonlinear Fano resonances that allows for the tunable unidirectional wave propagation and ultrahigh transmission contrast ratio. We further present a realistic photonic example which demonstrates the properties of nonreciprocity can be dynamically manipulated using a pump pulse, based on the general theoretical model. ; Comment: 7pages, 7figures