Here are some signs that your car may have a bad oxygen sensor:

This is the most common sign of a bad oxygen sensor.

Check engine light. This is the most common sign of a bad oxygen sensor. The check engine light is a warning light on your dashboard that indicates a problem with your car's engine.

Decreased fuel economy. A bad oxygen sensor can cause your car to lose fuel efficiency. This is because the sensor is not accurately measuring the air-fuel mixture.

Sulfur or gasoline smell from the exhaust. A bad oxygen sensor can cause a sulfur or gasoline smell from the exhaust.

Black smoke from the exhaust. Black smoke from the exhaust is another sign of a bad oxygen sensor. This is because the sensor is not accurately measuring the oxygen content in the exhaust

 Rough idle. A bad oxygen sensor can cause your car to have a rough idle. This is because the sensor is not accurately measuring the air-fuel mixture, which can lead to the engine running unevenly.

Failed emissions test. If your car fails an emissions test, it could be a sign of a bad oxygen sensor. The oxygen sensor is important for controlling emissions,