OBD-II is an expanded set of standards and practices developed by SAE and adopted by the EPA and CARB (California Air Resources Board) for implementation by January 1, 1996.

When did they start putting OBD2 in cars?

OBDII included a series of standardized diagnostic trouble codes (DTCs). 1996 — OBD-II becomes mandatory for all cars manufactured in the United States.

What year did OBD 3 start?

According to many car forums, obd3 will start to be on cars in 2012. They claim that the obd3 system will communicate to a central database that would require you to fix emmission type problems much quicker, eliminating the need for inspections. More information is on this site.