In “Riding The Waves,” in the August, 1994 Import Service, we discussed the basic principles used to identify and analyze sine waves, square waves and pulse signals. There is another type waveform that is used in vehicle electronics called a Pulse-Width-Modulated waveform, or “PWM” for short. A PWM is very similar in nature to a square wave signal. When viewed on an oscilloscope, both PWM and square waveforms look similar. Both have a horizontal HIGH and LOW trace, with vertical transitions connected HIGH and LOW portions of the signal.