We propose a novel approach of nonlinear resonant spectroscopy based on a collinear and degenerated pump probe experiment. This particular scheme leads to an oscillating time-resolved signal superimposed to the usual transient absorption signal. We have performed both amplitude and phase analysis of this oscillating signal as a function of the pump probe delay for different laser wavelengths. As an example, results on the resonantly excited dye molecule hexamethylindotricarbocyanine iodide (HITCI) in ethylene glycol at room temperature have been exploited in the framework of the phenomenological Brownian oscillator model. The corresponding numerical simulations have been carried out with a special emphasis on the phase sensitivity versus pump probe delay and detuning. The chromophore dynamical parameters obtained from phase variations of our signal are compared with other available spectroscopic studies.