Oxygen Sensor Before Catalytic Converter: Notes

The oxygen sensor before catalytic converter is a broadband oxygen sensor (control sensor). The broadband oxygen sensor continuously measures the residual oxygen in the exhaust gas. The fluctuating values of the residual oxygen are sent to the engine control unit as a voltage signal. The engine control corrects the mixture composition by changing the fuel injection. A new addition is the enhanced ADV LSU broadband oxygen sensor (Bosch). LSU stands for "universal oxygen sensor" and ADV for "Advanced".