Where are oxygen sensors located and do they have different purposes?
Oxygen sensors have been standard equipment on almost all passenger cars and light trucks with gasoline engines since 1980-1981. Most vehicles built before the mid-90s have one or two oxygen sensors (two were used on selected V6 and V8 engines starting in the late 1980s). Oxygen sensors are normally located in the exhaust system before the catalytic converter to measure exhaust emissions as they come from the engine combustion chambers. In 1996 with the federal mandated use of on-board-diagnostic systems (OBDII), vehicles also require additional oxygen sensors after the catalytic converter, to ensure that the converter is operating properly.
