Explains how to read the O2 sensor signal on the OBD-II scanner, Scope-1 or Scan-1. The O2 sensor generates a signal. A Scope-1 or automotive oscilloscope is then used to read the signal and an analysis is made. The proper analysis of the O2 sensor will determine its general condition or if a replacement is needed. This video also explain the O2 sensor operation and other ways to test it.