WS3-4

O2 sensor:
The O2 sensor works in comparing the amount of oxygen in the exhaust and amount oxygen in the ambient air ... above we can see the oxygen sensor is operational which normaly has to reach 300 deg/C and after that ECU goes in to closed loop which means the ECU uses oxygen sensor to see if the air/fuel mixture is lean or rich and if rich it will make it leaner and when lean it will make it rich and we can see this cycle in the above photo.