Following the introduction of on-board diagnostic (OBD) requirements in California, OBD regulations were also adopted by the US EPA. The following have been the most important steps in the development of federal OBD requirements:
- Beginning with the 1994 model year, the EPA has required OBD systems on light-duty vehicles (LDVs) and light-duty trucks (LDTs).
- Since 2005, OBD systems became mandatory for heavy-duty vehicles and engines up to 14,000 lbs GVWR.
- In December 2008, EPA finalized OBD regulations for 2010 and later heavy-duty engines used in highway vehicles over 14,000 lbs GVWR and made changes to the OBD requirements for heavy-duty applications up to 14,000 lbs GVWR to align them with requirements for applications over 14,000 lbs GVWR.