What does an Oxygen Sensor do?

What does an oxygen sensor do? Welcome to Mercie J Auto Care, where compassion and craftmanship come together. I’m Rick Smith, Master certified technician. Now the reason this question came up is because I have elderly parents and my wife and I were concerned about their oxygen levels and so she wanted to get one of those things that goes on your finger to measure the oxygen level in your blood, so she googled oxygen sensor. None of these came up, instead a vehicle oxygen sensor came up came up. What an oxygen sensor does is it actually gives feedback to the computer. So the computer commands a certain amount of fuel through the injectors to go into the engine, and then based on the amount of oxygen in the exhaust that tells us how much fuel was in there. Was it fully burned or was it too rich, too lean, that sort of thing, So we have an oxygen sensor to tell the computer, hey, are we running the right amount of fuel through the engine? Now, they can also be called air fuel ratio sensors, which are a little bit different. Bottom line is we have to have the right amount of fuel so that the car runs well and gets good fuel economy but also so the catalytic converter can work properly. We also put an oxygen sensor after the catalytic converter so we have upstream ones which are primarily the fuel control centers, and then we have the downstream ones which are after the catalytic converter and they’re primarily to tell us what the health of the catalytic converter is. So they are basically feedback sensors to tell the computer if everything is working well or not, and they sense the level of oxygen in the exhaust. Thanks for watching and util next time, safe travels and blessings to you.