Parts for your 2019 Nissan Pathfinder-Oxygen sensor

2019 Nissan Pathfinder oxygen sensor: what it does and when to replace it

Technical sources confirm the 2019 Nissan Pathfinder is fitted with oxygen-sensing hardware. The Nissan Factory Service Manual for the R52 (EC – Engine Control System) specifies upstream Air–Fuel Ratio (A/F) sensors and downstream Heated Oxygen Sensors (HO2S) on both banks of the 3.5‑litre V6. Nissan’s parts catalogues list these as separate upstream (A/F) and downstream (O2) units, and OBD‑II emissions rules require them for fuel control and catalytic converter monitoring. So yes, an oxygen sensor is absolutely relevant and used on the 2019 Pathfinder.

On this model, the upstream A/F sensors continuously measure exhaust oxygen so the engine control unit can keep the mixture right on the money. That tight lambda control helps the V6 run smoothly, save fuel, and keep emissions in check. The downstream O2 sensors sit after the catalytic converters and act like referees, confirming the cats are doing their job. If they spot poor conversion efficiency or out‑of‑whack readings, the check engine light pops on and a fault code is stored.

As part of regular servicing, it’s smart to have the sensors checked with a scan tool for fuel trims and response times. While many last well beyond 150,000 km, wideband A/F sensors are wear items and can slowly drift. Using quality fuel, fixing any exhaust leaks, and sorting misfires promptly all help the sensors and cats live longer.

When replacement time comes, match upstream vs downstream sensors to the correct bank, there are two of each on the V6. Go for OEM or equivalent quality. Warm the exhaust slightly to ease removal, use an O2 sensor socket, avoid contaminating the sensing tip, and route the harness exactly like factory so it won’t chafe or touch hot bits. After installation, clear codes and complete a proper drive cycle so the ECU can relearn. If a light returns, look for causes that can mimic a bad sensor—vacuum leaks, exhaust leaks, or a lazy catalytic converter.

• Common symptoms: worse fuel economy, rough idle, sulphur smell, failed emissions test/WOF, and fault codes like P0133, P0138, P0158, or P0420.
• Service tip: if an upstream A/F sensor is tired on a high‑km engine, consider replacing its pair on the opposite bank to keep trims balanced.

Popular questions

How many oxygen sensors does a 2019 Nissan Pathfinder have?
The V6 runs four in total—two upstream A/F sensors (one per bank) that control fuelling, and two downstream heated O2 sensors that monitor the catalytic converters. Using the right sensor type and fitting it to the correct bank is essential.

What are the signs an oxygen sensor needs replacing?
Owners often notice higher fuel use, a check engine light, a slightly rough idle, or a sulphur/rotten‑egg smell. Scan results may show slow sensor response or out‑of‑range fuel trims. It’s best to verify with diagnostics before replacing parts.

Can it be driven with a bad oxygen sensor?
Usually, the vehicle will still run, but it may use more fuel and could damage the catalytic converters over time. Prolonged driving with a faulty sensor can also trigger failed emissions checks and may mask other issues, so prompt repair is recommended.