Heated Oxygen Sensors (HO2S)

The front HO2S determines whether the air fuel mixture is too rich or too lean. It generates a voltage signal depending on oxygen content of exhaust gases. ECM uses inputs from front HO2S for calculating fuel mixture correction to fuel injector pulse width. Located in exhaust manifold(s). ECM uses input from rear HO2S to monitor effectiveness of Three Way Catalytic (TWC) converter. Located downstream from TWC converter.