1. Oxygen (O₂) Sensor Explained — What It Does, Where It Is & How to Check Air-Fuel Ratio In this detailed video we explain everything about the car oxygen (O₂) sensor — what it is, how it works, where it’s mounted, and how it helps the ECU control the air-fuel ratio (AFR). Whether you’re a DIY mechanic or a car enthusiast, this guide covers both theory and practical checks you can do with basic tools. Call to action (use in video & description): Like, subscribe and click the bell if you found t