Parts for your 2018 Honda Accord-Oxygen sensor

2018 Honda Accord oxygen sensor: what it does and when to replace it

Yes, the 2018 Honda Accord is fitted with oxygen sensors. Honda’s factory service information for the 10th‑gen Accord (PGM‑FI/engine control) specifies an upstream air‑fuel ratio (A/F) sensor and a downstream oxygen sensor for both the 1.5‑litre and 2.0‑litre turbo petrol engines, and the hybrid also uses exhaust oxygen sensing for catalyst monitoring. This aligns with OBD‑II requirements (SAE J1979) and local emissions rules (e.g., ADR 79/04 Euro 5 framework in Australia and equivalent NZ standards), which mandate upstream and downstream sensors to manage fuelling and check catalytic converter efficiency.

On the 2018 Accord, the upstream sensor (often called a wideband A/F sensor, Bank 1 Sensor 1) constantly reports how rich or lean the engine is running so the ECU can trim fuel on the fly for smooth performance, solid fuel economy and low emissions. The downstream sensor (Bank 1 Sensor 2) sits after the catalytic converter and keeps an eye on catalyst health. Together they help the Accord start clean when cold, cruise efficiently on the motorway and pass emissions testing without drama.

There’s no set “time‑based” replacement interval in normal servicing, these sensors are typically replaced when symptoms or fault codes point to a problem. Common signs include a Check Engine light, higher fuel use, rough idle, hesitation, sulphur/rotten‑egg smells, or codes such as P0134, P0135, P0138, or P0420. If those crop up, proper diagnosis with live data (upstream lambda close to 1.0, downstream switching behaviour, fuel trims) is the way to go.

When replacement is needed, sticking with quality OEM‑equivalent parts (Honda/Denso/NTK) avoids headaches. The upstream A/F sensor is more sensitive and pricier than the downstream unit, and mixing up connectors or universal wire splices can cause drivability gremlins. A few practical tips:

• Let the exhaust cool and use a proper O2‑sensor socket to avoid rounding.
• Most new sensors come with anti‑seize on the threads, if not, use a sensor‑safe compound sparingly and keep it off the tip.
• Follow Honda repair data for torque, wire routing and connector handling.
• Clear codes and perform a short drive cycle so the ECU can relearn trims and run catalyst monitors.

As preventive care, fix any exhaust leaks, misfires, or oil/coolant consumption quickly—those issues contaminate sensors and the cat. For anyone chasing better economy or a smoother idle, verifying sensor performance during routine servicing is a low‑cost win.

How many oxygen sensors does a 2018 Honda Accord have?

Non‑hybrid petrol models typically have two: one upstream A/F sensor before the catalytic converter and one downstream oxygen sensor after it. Variants and market specs can differ slightly, but the two‑sensor layout is standard for OBD‑II.

What are the signs an oxygen sensor is failing on a 2018 Accord?

Look for a Check Engine light, worse fuel economy, rough idle, hesitation, or a strong exhaust smell. Scan tools may show codes like P0134 or P0420 and odd fuel trims. If in doubt, have a technician confirm with live data.

Can it be driven with a bad oxygen sensor?

Short term, the car will usually run, but it may use more petrol, feel a bit off, and risk catalyst damage if left too long. It’s best to diagnose and repair promptly to protect the catalytic converter and keep rego inspections hassle‑free.