This document provides an overview of On-Board Diagnostics (OBD) II systems and how to use an automotive scan tool. It describes key OBD II concepts like Diagnostic Trouble Codes, readiness monitors, and the various OBD II modes of operation. The document also provides instructions on navigating the scan tool user interface and performing functions like reading and erasing codes and viewing live data. Safety precautions are outlined at the beginning for using scan tools when working on vehicles.