How many oxygen sensors does a Lexus RX350 have?
The Lexus RX350 typically uses four oxygen sensors—two upstream before the catalytic converters and two downstream after them—to monitor exhaust gas and help the engine control unit optimize fuel and emissions.
Overview of the four O2 sensors in the RX350
The RX350 is powered by a 3.5-liter V6 engine arranged across two banks. Each bank houses an upstream (pre-cat) sensor and a downstream (post-cat) sensor, totaling four conventional oxygen sensors. This setup is standard across most RX350 generations, though some model years may include additional air-fuel ratio sensors in the emissions system that are not counted among the four O2 sensors.
The following outlines the four conventional O2 sensors and where they sit in the exhaust system:
- Bank 1 Sensor 1 — Upstream sensor located before the catalytic converter on Bank 1.
- Bank 1 Sensor 2 — Downstream sensor located after the catalytic converter on Bank 1.
- Bank 2 Sensor 1 — Upstream sensor located before the catalytic converter on Bank 2.
- Bank 2 Sensor 2 — Downstream sensor located after the catalytic converter on Bank 2.
In practice, four O2 sensors is the standard count for the RX350. If you’re replacing them, ensure you match the correct bank and upstream/downstream position to avoid diagnostic and performance issues.
Additional considerations
Some late-year models or certain trims may include an additional air-fuel ratio (AFR) sensor as part of a direct-injection system. This AFR sensor is not counted among the standard four O2 sensors, but it can appear in the exhaust-management setup. When in doubt, consult the vehicle’s service manual for the exact sensor configuration by model year.
Summary
For most Lexus RX350 models, expect four conventional oxygen sensors: Bank 1 Sensor 1 and Sensor 2, plus Bank 2 Sensor 1 and Sensor 2. These sensors provide essential feedback to the engine control unit to regulate fuel mixture and emissions. Always verify the exact arrangement for your specific model year if performing replacement or diagnostic work.
