What is OBD-II?
Quick Answer
OBD-II provides standardized access to emissions-related diagnostic information; a code is a starting point for diagnosis.
OBD-II is the second generation of on-board diagnostics. In the United States it became required for most model-year 1996 and later passenger cars and light-duty vehicles. It standardizes access to emissions-related diagnostic information through a diagnostic connector. A stored code describes an observation; it does not establish a failed part. Not every body, chassis or communication code illuminates the check engine light.