Parts for your 2021 Lexus Is-Oxygen sensor

2021 Lexus IS Oxygen Sensor – Purpose, Service Tips, and When to Replace

Technical sources including the Lexus Repair Manual (TIS) for the 2021 IS, plus Toyota engine documentation for the 8AR‑FTS (2.0‑litre turbo) and 2GR‑FKS (3.5‑litre V6), confirm the model uses oxygen-sensing hardware: wideband air‑fuel ratio (A/F) sensors before the catalytic converters and conventional O2 sensors after them. These are integral to OBD‑II emissions control and ADR 79/04 compliance, so an oxygen sensor is absolutely relevant and fitted on the 2021 Lexus IS.

On this IS, the upstream A/F sensor constantly reads exhaust oxygen content to help the ECU fine‑tune the air–fuel mixture for smooth performance, good fuel economy, and low emissions. The downstream O2 sensor monitors catalytic converter efficiency. If either goes out of range, the car can run rich or lean, burn more fuel, feel a bit doughy, and risk damaging the cat. The V6 has two banks, so typically four sensors (two A/F, two O2). The four‑cylinder has a single bank with two sensors (one A/F, one O2).

While these sensors are “fit and forget” for years, they are wear items. Many workshops suggest inspection around 150,000–200,000 kilometres or earlier if there are symptoms. Lexus scan data and fault codes (think P013x, P015x, P017x, P0420/P0430) are the go‑to indicators for action. Using OEM‑quality sensors (often Denso for Lexus) keeps the readings accurate and avoids headaches with trims and drivability.

• Common signs it’s time: noticeable drop in fuel economy, check engine light, rough idle, sulphur/rotten‑egg smell, or failed emissions test.
• Service tips: let the exhaust cool, use penetrating oil on threads, and fit with a new crush washer. Tighten to Lexus spec (about 40–44 N·m, sensor‑dependent) and avoid twisting the harness.
• Post‑fit: clear codes, reset fuel trims if needed, and road‑test to confirm closed‑loop operation is stable.

A/F (upstream) sensors tend to drift gradually, swapping a lazy one can restore sharp throttle response and smarter fuel use. Downstream O2 sensors mostly validate catalyst health, a weak reading there can trigger cat codes even when the converter is fine. If one sensor on a high‑kilometre bank fails, some prefer replacing the pair on that bank to keep readings consistent, but it’s not mandatory if data shows only one is out.

How many oxygen sensors does a 2021 Lexus IS have?

The 2.0‑litre turbo four usually has two sensors: one upstream A/F sensor and one downstream O2 sensor. The 3.5‑litre V6 typically has four: two A/F sensors (one per bank) and two downstream O2 sensors.

When should the oxygen sensors be replaced?

They’re replaced when faults are logged, performance or economy drops, or a workshop confirms slow or biased readings. Many owners consider proactive replacement between 150,000 and 200,000 kilometres, especially for upstream A/F sensors.

Can the Lexus IS be driven with a bad oxygen sensor?

Short distances may be okay, but extended driving risks poor fuel economy, rough running, and potential catalyst damage. It’s best to diagnose and fix promptly.