Front Air‑Fuel Ratio Sensor for Subaru

This premium upstream AFR (wideband oxygen) sensor keeps your Subaru’s engine breathing right. It constantly tells the ECU how much oxygen is in the exhaust so the mixture stays near stoichiometric. Result: smooth idle, strong response, clean emissions, and smart fuel use ⛽.

Why you need it

Correct air‑fuel control protects the catalytic converter, prevents carbon build‑up, and stabilizes cold starts. A healthy sensor maximizes mileage and keeps the check engine light off.

How it works

Inside is a zirconia wideband cell and integrated heater. The heater brings the tip to operating temp fast, then the ECU adjusts fuel by reading the sensor’s pump current. This closed‑loop feedback trims mixture in milliseconds for precise control at idle, cruise, and load.

When it fails ⚠️

Expect rough idle, hesitation, high fuel use, fuel smell, and stored lean/rich codes. Long term, an over‑rich mix can overheat the catalyst; over‑lean can cause misfire and power loss. Replace promptly to avoid costly exhaust repairs.

Tech tips

Install on the upstream bung, route the harness away from heat, use proper anti‑seize, and torque to spec. Clear codes and allow a short ECU relearn drive.

Compatibility

• Impreza
• Xv
• Forester
• Exiga