What is a Car Code Reader? A car code reader is one of the simplest car diagnostic tools that you'll find. These devices are designed to interface with a car's computer and report trouble codes in a very no-frills sort of way. Cars and trucks that were built prior to 1996 require specific, proprietary OBD-I code readers, and newer vehicles use universal OBD-II code readers. This type of car code reader is typically inexpensive, and some parts stores and shops will even read your codes for free. How Does a Car Code Reader Work? Computer controls started to show up on cars in the late 1970s and early 1980s maxidiag elite md802 updates, and these systems rapidly grew in complexity. Even very early computer controls included basic "on board diagnostic" functionality, and these early, OEM-specific systems are collectively referred to as OBD-I. In 1995, for the 1996 mod ... Read more »