Air-Fuel Ratio Sensor
A wideband oxygen sensor that measures the exact ratio of air to fuel in the exhaust gases for precise engine tuning.
An Air-Fuel Ratio (AFR) sensor, also known as a wideband oxygen sensor, is an advanced emission control device mounted in the exhaust manifold. While standard O2 sensors only tell the ECU if the mixture is rich or lean, the AFR sensor measures the exact air-fuel ratio.
The sensor outputs a linear signal that allows the Engine Control Unit (ECU) to calculate the precise fuel-to-air ratio across a wide range (from extremely rich to very lean). This allows the ECU to make rapid, micro-adjustments to fuel injector timing, optimizing combustion.
AFR sensors are critical for modern vehicles to meet strict emissions standards and maximize fuel economy. They are also widely used in turbocharged and performance engines where maintaining a precise fuel mixture under load is essential to prevent engine knock.
Like standard oxygen sensors, AFR sensors can become fouled by carbon, oil, or coolant. A failing sensor leads to poor fuel economy, engine hesitation, and a Check Engine Light with diagnostic codes.