An electrosurgical generator, comprising: an RF output stage configured to supply electrosurgical energy to tissue via at least one active electrode configured to apply electrosurgical energy to tissue; sensing circuitry configured to measure impedance of tissue; wherein the sensing circuit is further configured to measure phase between voltage and current waveforms of the electrosurgical energy delivered to the tissue; and a controller configured to: determine whether a tissue reaction has occurred as a function of a minimum impedance value and a predetermined rise in impedance, wherein tissue reaction corresponds to a boiling point of tissue fluid; generate a target impedance trajectory as a function of measured impedance and desired rate of change based on the tissue reaction determination, wherein the target impedance trajectory includes a plurality of target impedance values; drive tissue impedance along the target impedance trajectory by adjusting the output level of the electrosurgical generator to substantially match tissue impedance to a corresponding target impedance value for at least a predetermined minimum time period; compare the measured phase to a lower phase threshold; compare the measured phase to an upper phase threshold; detect an open circuit if the measured phase is above the upper phase threshold; and detect a short circuit if the measured phase is below the lower phase threshold. an RF output stage configured to supply electrosurgical energy to tissue via at least one active electrode configured to apply electrosurgical energy to tissue; sensing circuitry configured to measure impedance of tissue; wherein the sensing circuit is further configured to measure phase between voltage and current waveforms of the electrosurgical energy delivered to the tissue; and a controller configured to: determine whether a tissue reaction has occurred as a function of a minimum impedance value and a predetermined rise in impedance, wherein tissue reaction corresponds to a boiling point of tissue fluid; generate a target impedance trajectory as a function of measured impedance and desired rate of change based on the tissue reaction determination, wherein the target impedance trajectory includes a plurality of target impedance values; drive tissue impedance along the target impedance trajectory by adjusting the output level of the electrosurgical generator to substantially match tissue impedance to a corresponding target impedance value for at least a predetermined minimum time period; compare the measured phase to a lower phase threshold; compare the measured phase to an upper phase threshold; detect an open circuit if the measured phase is above the upper phase threshold; and detect a short circuit if the measured phase is below the lower phase threshold. determine whether a tissue reaction has occurred as a function of a minimum impedance value and a predetermined rise in impedance, wherein tissue reaction corresponds to a boiling point of tissue fluid; generate a target impedance trajectory as a function of measured impedance and desired rate of change based on the tissue reaction determination, wherein the target impedance trajectory includes a plurality of target impedance values; drive tissue impedance along the target impedance trajectory by adjusting the output level of the electrosurgical generator to substantially match tissue impedance to a corresponding target impedance value for at least a predetermined minimum time period; compare the measured phase to a lower phase threshold; compare the measured phase to an upper phase threshold; detect an open circuit if the measured phase is above the upper phase threshold; and detect a short circuit if the measured phase is below the lower phase threshold.