An oxygen sensor, also known as an 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 combustion chamber. The correct air-fuel ratio is important for ensuring that the engine runs efficiently and produces the correct amount of power.
There are two main types of O2 sensors: heated and unheated. Heated O2 sensors are used in most modern vehicles. They are heated to a high temperature, which allows them to reach their operating temperature quickly and to respond quickly to changes in the exhaust gas composition. Unheated O2 sensors are used in older vehicles. They do not have a heating element, so they take longer to reach their operating temperature and are not as responsive to changes in the exhaust gas composition.