Upstream Air‑Fuel Ratio Sensor (Wideband) for Toyota Engines

Why you need it

This AFR sensor constantly measures oxygen in exhaust to keep the mix near ideal. With correct data, the ECU trims fuel precisely, giving smooth power, lower emissions, and better mpg ⛽. It also protects the catalytic converter by preventing rich or lean burn that overheats the cat and wastes fuel .

How it works

A heated planar cell reaches temperature fast and reads oxygen content as a current signal. The ECU interprets this wideband signal and adjusts injector pulse width in real time. Located before the catalytic converter (upstream),it reacts quickly to throttle changes and cold starts .

If it fails

Expect rough idle, flat spots, high fuel use, sulfur smell, and a Check Engine Light (often lean/rich codes). Emissions rise, the cat can be damaged, and inspection may fail ⚠️. Replace promptly. Install on a cool exhaust, use the correct socket, avoid touching the tip, and tighten to factory spec.

Compatibility

• Grand Highlander
• Highlander
• Highlander/Kluger
• Rav4
• Sienna