How many O2 sensors does a Lexus ES300 have?
The typical ES300, powered by a 3.0-liter V6, uses four oxygen sensors in total—two upstream sensors that read exhaust gas before the catalytic converters, and two downstream sensors after the converters, one on each bank of the engine.
Oxygen sensor layout in the ES300
Here's how the sensors are arranged on the ES300's exhaust system and what each one monitors.
- Bank 1 Upstream (pre-cat, O2 Sensor 1): Senses the oxygen content of exhaust before the catalytic converter on one bank.
- Bank 1 Downstream (post-cat, O2 Sensor 2): Monitors catalytic converter efficiency after the same bank's catalyst.
- Bank 2 Upstream (pre-cat, O2 Sensor 3): Senses exhaust before the catalyst on the other bank.
- Bank 2 Downstream (post-cat, O2 Sensor 4): Monitors catalytic converter efficiency after the other bank's catalyst.
In practice, you may see sensor numbering differ in repair manuals, but the four-sensor setup is standard for the ES300 V6 with dual catalysts.
Model years and engine notes
The four-sensor configuration corresponds to the 3.0-liter V6 used in most ES300 models (notably the 1MZ-FE engine family). Some markets or very early/late variants could have variations, but four sensors remain the norm for stock ES300 vehicles with the traditional V6 and dual catalytic converters. If you are unsure, consult the factory service manual for your exact year and VIN.
Summary
For a typical Lexus ES300 with the 3.0L V6, expect four oxygen sensors—two before and two after the catalytic converters, one on each exhaust bank. This arrangement supports accurate air-fuel monitoring and catalytic converter performance across most model years.
