Oxygen Sensor: Description and Operation

The upstream Heated Oxygen Sensor (HO2S) is mounted in the exhaust manifold and senses the oxygen concentration in the exhaust gas. It sends this information to the powertrain control module, which uses the information to determine fuel injection amounts. The sensing element is made of zirconia ceramic with a platinum coating.

The downstream heated oxygen sensor is mounted on the muffler inlet pipe just below the Three Way Catalytic Converter (TWC). The downstream heated oxygen sensor monitors the three way catalytic converter and transmits the information to the powertrain control module.