The ECU that controls the engine in your street car and racecar requires information to make decisions, and an important piece of that data pie is the engine’s air/fuel ratio (AFR). An Oxygen sensor (O2 sensor) lives in the exhaust system and measures for AFR as the engine runs. In this video from Haltech, we get an education on O2 sensors and how they work.

There are two types of O2 sensors; a narrowband, and a wideband style — each has a different measurement ability. The narrowband O2 sensor has a limited range of AFR measurement, and can only send a signal to the ECU while it’s in the closed-loop AFR range. A wideband O2 sensor will measure a broader range of AFRs, and it can provide a more accurate measurement of the exhaust gasses to the ECU.

The wideband O2 sensor’s wider range of measurement allows the ECU to make adjustments so it can match the AFRs the tuner wants. These wideband O2 sensors make long term learning possible; this means the ECU can use the AFR information provided by the sensor to improve the overall tune of the engine. There’s a lot of different factors that can cause AFRs to differ, so having the ability to make long-term tuning changes is important to street cars.

The wideband can also be used to set a failsafe so an engine will go into limp mode if there’s an issue. This type of protection can save an expensive high-performance engine if there’s a problem with the fuel system or if another type of issue occurs.

Haltech offers a wide range of O2 sensors and you can see them all right here on the company’s website.