An oxygen sensor (O2 sensor) is a device that measures the amount of oxygen in the exhaust gases of an internal combustion engine. This information is used by the engine’s electronic control unit (ECU) to adjust the air-fuel ratio, which is the ratio of air to fuel in the engine’s cylinders. The correct air-fuel ratio is important for ensuring that the engine runs efficiently and produces the correct amount of power.
O2 sensors are typically located in the exhaust manifold or exhaust pipe, where they are exposed to the exhaust gases. The sensor consists of a ceramic element that is coated with a thin layer of platinum or other noble metal. When the exhaust gases pass over the ceramic element, the oxygen in the gases reacts with the metal coating, causing an electrical signal to be generated. The strength of the electrical signal is proportional to the amount of oxygen in the exhaust gases.