A surgical instrument for coagulating and dissecting tissue, the surgical instrument comprising: a processor; an end effector at a distal end of the surgical instrument, the end effector configured to interact with tissue, the end effector comprising: a clamp arm comprising an electrode; an ultrasonic blade; an ultrasonic transducer acoustically coupled to the ultrasonic blade and configured to receive a drive signal from a generator to cause ultrasonic motion of the ultrasonic blade and deliver ultrasonic energy to the ultrasonic blade; wherein the processor is configured to: control delivery of radio frequency energy to the electrode; transition from delivery of the RF energy to the electrode to delivery of the ultrasonic energy to the ultrasonic blade; control delivery of an exploratory ultrasonic pulse to the ultrasonic transducer; measure an ultrasonic property of tissue engaged by the end effector, wherein the ultrasonic property measured by the processor is associated with the exploratory ultrasonic pulse; determine whether the ultrasonic property measured by the processor is consistent with a behavior of low impedance tissue when the exploratory ultrasonic pulse is delivered to the ultrasonic transducer and corresponding ultrasonic energy is delivered to the ultrasonic blade; determine whether a short circuit has occurred when the ultrasonic property measured by the processor is not consistent with the behavior of low impedance tissue when ultrasonic energy is applied to the tissue; control delivery of the ultrasonic energy to the ultrasonic blade to cut the tissue upon determining that the ultrasonic property measured by the processor is consistent with ultrasonic energy being applied to low impedance tissue; and upon determining that a short circuit has occurred, cease delivery of the ultrasonic energy to the surgical instrument. a processor; an end effector at a distal end of the surgical instrument, the end effector configured to interact with tissue, the end effector comprising: a clamp arm comprising an electrode; an ultrasonic blade; a clamp arm comprising an electrode; an ultrasonic blade; an ultrasonic transducer acoustically coupled to the ultrasonic blade and configured to receive a drive signal from a generator to cause ultrasonic motion of the ultrasonic blade and deliver ultrasonic energy to the ultrasonic blade; wherein the processor is configured to: control delivery of radio frequency energy to the electrode; transition from delivery of the RF energy to the electrode to delivery of the ultrasonic energy to the ultrasonic blade; control delivery of an exploratory ultrasonic pulse to the ultrasonic transducer; measure an ultrasonic property of tissue engaged by the end effector, wherein the ultrasonic property measured by the processor is associated with the exploratory ultrasonic pulse; determine whether the ultrasonic property measured by the processor is consistent with a behavior of low impedance tissue when the exploratory ultrasonic pulse is delivered to the ultrasonic transducer and corresponding ultrasonic energy is delivered to the ultrasonic blade; determine whether a short circuit has occurred when the ultrasonic property measured by the processor is not consistent with the behavior of low impedance tissue when ultrasonic energy is applied to the tissue; control delivery of the ultrasonic energy to the ultrasonic blade to cut the tissue upon determining that the ultrasonic property measured by the processor is consistent with ultrasonic energy being applied to low impedance tissue; and upon determining that a short circuit has occurred, cease delivery of the ultrasonic energy to the surgical instrument. control delivery of radio frequency energy to the electrode; transition from delivery of the RF energy to the electrode to delivery of the ultrasonic energy to the ultrasonic blade; control delivery of an exploratory ultrasonic pulse to the ultrasonic transducer; measure an ultrasonic property of tissue engaged by the end effector, wherein the ultrasonic property measured by the processor is associated with the exploratory ultrasonic pulse; determine whether the ultrasonic property measured by the processor is consistent with a behavior of low impedance tissue when the exploratory ultrasonic pulse is delivered to the ultrasonic transducer and corresponding ultrasonic energy is delivered to the ultrasonic blade; determine whether a short circuit has occurred when the ultrasonic property measured by the processor is not consistent with the behavior of low impedance tissue when ultrasonic energy is applied to the tissue; control delivery of the ultrasonic energy to the ultrasonic blade to cut the tissue upon determining that the ultrasonic property measured by the processor is consistent with ultrasonic energy being applied to low impedance tissue; and upon determining that a short circuit has occurred, cease delivery of the ultrasonic energy to the surgical instrument.