SEN AY-A/F RATIO

Front Air‑Fuel Ratio Sensor (Wideband O2) ️

This front air‑fuel ratio sensor keeps the engine in precise closed‑loop control. By tracking oxygen in the exhaust, it helps the ECU hit the ideal mixture for smooth power, low emissions, and great mileage. Perfect for Subaru applications that demand quick warm‑up and accurate mixture control in all weather. ⚙️

Why this part is needed

It stabilizes idle, improves throttle response, protects the catalytic converter, and reduces fuel use. Accurate AFR feedback means cleaner combustion and longer engine life.

How it works

A heated wideband element uses a pump cell to maintain a tiny reference oxygen level. The ECU reads the pump current/voltage to know if the mix is rich or lean and adjusts injector pulse instantly. A fast heater brings the sensor online within seconds for reliable control.

What happens if it fails ⚠️

Expect rough idle, sluggish pick‑up, high fuel consumption, sulfur smell, and a check engine light (common AFR/O2 codes). Long term, the catalyst can overheat and emissions rise. Replace promptly to pass inspections and restore performance. ⛽

Compatibility

• Impreza
• Xv
• Forester
• Exiga