@bfrosh001: But what happens when the oxygen sensor goes bad? How do you know if you have a bad oxygen sensor? Here are some common symptoms to watch out for: 1. **Check Engine Light**: If this light is on, it could indicate a problem with the oxygen sensor. 2. **Poor Fuel Economy**: A failing sensor can lead to increased fuel consumption. 3. **Rough Idling**: If the engine is idling unevenly, it may be due to a problematic sensor. 4. **Failed Emissions Test**: A malfunctioning oxygen sensor can cause your vehicle to fail emissions testing. If you're experiencing any of these signs, it might be time to have it checked out.