OBDII is an acronym for On board Diagnostics Second generation. It is a system that monitors and reports engine and transmission data. It also is responsible for illuminating the CEL or check engine light. The first generation of OBD was introduced in 1991 and was only mandatory for vehicles sold in California. It was up to the discretion of the manufacturer as to what communication protocol, port, and trouble codes were to be used. In an effort to make things more uniform the EPA made it mandatory for all vehicles sold in the US to have OBDII starting for the 1996 model year. The OBDII specification has a standard port location, port, and list of DTCS or diagnostic trouble codes. The OBDII port is located on the lower left side of the dash by the drives left knee.
