Parts for your 2015 Lexus Is-Oxygen sensor

2015 Lexus IS Oxygen Sensor: Purpose, Fitment and Servicing Advice

Technical sources confirm the 2015 Lexus IS range is fitted with oxygen-sensing hardware. The Lexus/Toyota Repair Manual (SFI system), the Electrical Wiring Diagram, and the Toyota/Lexus parts catalogue specify upstream air–fuel ratio (A/F) sensors and downstream oxygen (O2) sensors on 2015 IS models. V6 variants (IS250/IS350, chassis codes GSE30/31/35/36/37) use two A/F sensors and two O2 sensors (one pair per bank), while the IS300h hybrid (AVE30) typically uses one A/F sensor and one O2 sensor. This aligns with OBD‑II and ADR/Euro emissions requirements of the era, which mandate monitoring before and after the catalytic converter.

On the 2015 Lexus IS, the oxygen-sensing system constantly checks how much oxygen is in the exhaust. The upstream A/F sensors (wideband) let the engine computer trim fuel precisely for smooth running and good fuel economy, while the downstream O2 sensors keep tabs on catalytic converter efficiency. Together, they help the car run clean, save petrol, and avoid that dreaded check engine light.

There’s no fixed replacement interval on these sensors—they’re usually replaced when faulty. Still, after high kilometres (often 160,000–200,000 km+), they can grow sluggish. If fuel use creeps up, idle goes a bit lumpy, or the car fails a WOF/rego emissions test, it’s worth scanning for codes and looking at live fuel trims. Common signs include:

• Check engine light with codes like P0138, P0137, P2195, P2197, P0420
• Heavier petrol use, sooty tailpipe, or a whiff of sulphur/rotten egg
• Hesitation, rough idle, or poor cold starts

When replacement’s on the cards, use the correct type: Toyota/Lexus call the upstream units “Air–Fuel Ratio Sensors” and the downstream units “Oxygen Sensors”. Quality OEM-spec (often Denso) is the safe bet. Many new sensors come pre-coated on the threads, avoid extra anti-seize unless specified, as it can affect torque and grounding. Always follow the Lexus torque spec from the repair manual and use an O2 sensor socket. Work on a cool exhaust, route the harness exactly as factory, and clip it away from heat and moving parts.

Good servicing practice is to rule out exhaust leaks ahead of the sensor and any intake or vacuum leaks—they can skew readings and lead to misdiagnosis. After fitting, clear codes, reset fuel trims, and complete a proper drive cycle so the ECU relearns. For V6 models with four sensors, diagnose by bank and sensor position (Bank 1/2, Sensor 1/2) to avoid replacing the wrong unit. Look after these little guys and the IS will stay frugal, punchy, and emissions-compliant.

How many oxygen sensors does a 2015 Lexus IS have?

It depends on the engine. IS250 and IS350 V6 models have four sensors—two upstream A/F sensors (one per bank) and two downstream O2 sensors. The IS300h hybrid typically uses one upstream A/F sensor and one downstream O2 sensor.

When should the oxygen sensors be replaced on a 2015 Lexus IS?

They’re not a routine “time-based” service item. Replace when they fail or readings become slow or erratic. Many last beyond 160,000 km. If fuel economy drops, a check engine light appears, or emissions testing flags a fault, inspect and test before replacing.

Can a bad oxygen sensor damage the catalytic converter?

Yes. A faulty sensor can cause the engine to run rich, which can overheat and poison the cat over time. Sorting sensor issues early helps protect the converter and keeps the IS running efficiently.