What is the difference between OBD1 and OBD2 auto?

The first generation of OBD systems – known as “OBD1” – 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, OBD1 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 2,” “Global OBD II” or “Generic OBD 2” – are part of a system the Society of Automotive Engineers (SAE) developed to regulate automotive electronic diagnosis. OBD 2 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 2 compliant vehicle without special adapters or manufacturer-specific tools which are necessary for OBD1 vehicles.

OBD II systems are more sophisticated than OBD1 – 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.