Abstract: A novel method in accordance with the invention for generating diagnostic signals for power plants (e.g., automobile engines and other internal combustion engines, gas turbines, and the like) utilizes a digital storage lab oscilloscope (DSO), configured to display at least about five seconds of data at about at least 50 data points per second, to capture specific power plant information primarily from an oxygen sensor. A preliminary waveform analysis verifies that the oxygen sensor is functioning correctly. Then, the oxygen-sensor waveform is classified as to certain primary characteristics to produce gross-level diagnostic information. If necessary, the injector waveform can be used to further classify system or mechanical malfunctions. More specific diagnostic information is obtained by classifying certain secondary characteristics of the waveform.