How many O2 sensors does a 2008 Lexus is250 have?
The 2008 Lexus IS250 uses four oxygen sensors.
In this model, the exhaust system is arranged in two banks. Each bank has an upstream sensor that monitors exhaust before the catalytic converter and a downstream sensor that checks catalyst efficiency after it, for a total of four sensors.
Sensor layout and count
The IS250’s exhaust is designed with two banks (Bank 1 and Bank 2). Each bank has one upstream O2 sensor and one downstream O2 sensor, resulting in a total of four sensors.
Bank-wise placement
For reference, upstream sensors monitor the air-fuel mixture before the catalytic converter, while downstream sensors verify catalytic performance after the converter.
To help with identification, the four sensors are listed by bank and position:
- Bank 1 Upstream (pre-cat)
- Bank 1 Downstream (post-cat)
- Bank 2 Upstream (pre-cat)
- Bank 2 Downstream (post-cat)
In short, there are four O2 sensors in the 2008 IS250—two before and two after the catalysts, across both banks. Accurate diagnosis and replacement require referencing the bank and sensor position.
Maintenance implications
O2 sensors influence fuel economy, emissions, and idle quality. If you see a check-engine light or symptoms like misfires, rough running, or poor mileage, a failed or aging O2 sensor may be the cause. Replacement intervals vary with driving conditions, but upstream sensors are commonly evaluated around the 60,000–100,000 mile range, with downstream sensors following similar considerations. Always consult the owner's manual or a qualified technician for codes specific to your vehicle.
Summary
The 2008 Lexus IS250 uses four O2 sensors—two upstream and two downstream—across its dual-bank exhaust. Knowing their layout aids diagnosis and maintenance, helping keep the vehicle efficient and emissions-compliant.
