Oxygen Sensor: Description and Operation

Fig. 6 Lambda sensor, typical installation.:

One sensor is incorporated onto each branch of the exhaust system near the catalyst. The lambda sensors, Fig. 6, are internally coated with a thin platinum layer which resists the exhaust gas. A ceramic layer protects the electrodes against corrosion and becomes a conductive layer to oxygen at approximately 1112°F. A voltage is generated between the two surfaces when the concentration of oxygen inside the sensor differs from that outside of the sensor. This voltage is transmitted to the E.C.U. which compares the transmitted voltage to a reference voltage for ideal combustion. The lambda sensors are a closed loop type control system. If the lambda sensors become inoperative or become disconnected, the E.C.U. will continue to function as an open loop system.