The first generation of OBD systems - known as "OBD I" - was introduced in 1981. Because each vehicle manufacturer developed its own system, there was no standardization among this generation of technology.

As a result, manufacturer-specific OBD I systems required a variety of diagnostic software and hardware. In general, OBD I vehicles were built through model year 1995.

In search of a better solution, the Environmental Protection Agency (EPA) later established standards for improved vehicle diagnostics. The resulting standards -- known as "OBD II," "Global OBD II" or "Generic OBD II" - are part of a system the Society of Automotive Engineers (SAE) developed to regulate automotive electronic diagnosis. OBD II is required for all vehicles (imported and domestic) sold in the U.S. beginning in 1996 which dictates the use of a common diagnostic link connector and software for monitoring fuel and emission systems. Technicians are able to use the same tool to test any OBD II compliant vehicle without special adapters or manufacturer-specific tools which are necessary for OBD I vehicles. This allows one tool design to connect with any passenger vehicle sold in the U.S. after 1996, thereby ensuring greater convenience and lower cost for tool manufacturers, technicians and DIYers.

OBD II systems are more sophisticated than OBD I - they seek out potential problems sooner and alert the driver to these issues through the "Check Engine" light or Malfunction Indicator Light (MIL). By alerting the owner of malfunctions as they occur, repairs can be sought promptly, which results in fewer emissions from the vehicle.

The following AutoXray products are OBD-I and OBD-II compatible: EZ-Scan 5000, EZ-Scan 5100, EZ-Scan 6000, EZ-Scan 6100 and EZ-Link 35000.

The following AutoXray products OBD-II compatible: EZ-Scan 4000, CodeScout 1500, CodeScout 700 and EZ-Link 10150.