P0420 on a 2023 Nissan Rogue

P0420 means the downstream oxygen sensor pattern suggests the bank 1 catalytic converter is not storing oxygen properly.

Not your vehicle? See general P0420 info.

Most common causes on the 2023 Nissan Rogue

Ranked from 660 NHTSA owner complaints filed for this vehicle.

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1
Oil or coolant contamination of the catalytic converter
High severity
Documented oil-burning/metal-shavings-in-oil and a coolant leak smelled from the exhaust on this engine can coat and poison the catalyst, dropping its efficiency; confirm with an oil-consumption check and a tailpipe smell/visual check.
Reported in 2 NHTSA complaints
Parts:catalytic converter
2
Worn or clogged catalytic converter
Medium severity
One owner was quoted for catalytic converter replacement without a proper exhaust restriction (clog) test being performed first; have backpressure/efficiency verified before replacing.
Reported in 1 NHTSA complaint
Parts:catalytic converter
3
Failing downstream (post-catalyst) oxygen sensor
Low severity
A lazy or biased rear O2 sensor can trip a false catalyst-efficiency code even with a healthy converter; compare upstream/downstream sensor switching on a scan tool.
Common cause
Parts:oxygen sensor
4
Exhaust leak upstream of the downstream O2 sensor
Low severity
A leaking manifold gasket, flange, or pipe joint ahead of the rear sensor draws in outside air and skews the catalyst monitor; smoke-test or listen for a hiss under load.
Common cause
Parts:exhaust gasket
5
Accumulated engine misfires or rough running overheating the catalyst substrate
Medium severity
Repeated rough-idle/stall events reported on this 1.5L VC-Turbo push unburned fuel into the exhaust and can thermally damage the converter over time.
Common cause
6
Turbocharger seal failure allowing oil into the exhaust stream
Medium severity
Turbo bearing/seal wear (widely reported on this engine's recall history) lets oil pass into the exhaust, fouling the catalyst; check for oily residue at the turbo outlet or tailpipe.
Common cause
Parts:turbocharger
7
PCM software calibration causing a false catalyst-efficiency reading
Low severity
An outdated engine control software calibration can misread normal catalyst aging as a failure; check for an applicable manufacturer reflash/TSB before replacing parts.
Common cause

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These causes are aggregated from NHTSA owner complaints and general repair knowledge — this is not a diagnosis. P0420 on your car still needs shop confirmation before any repair.

Common symptoms

Check engine light
Usually no drivability issue
Failed emissions test
Sulfur smell in some cases
Reduced power if converter is clogged

What to check before replacing parts

Check for misfire and fuel trim codes first

Look for: Any active or recent misfire, or lean/rich trim codes, means raw fuel or an off mixture has likely already damaged or is currently overworking the converter — fix those before touching the catalyst.

Inspect for exhaust leaks ahead of the converter

Look for: A leak before the converter (cracked manifold, loose flange, blown gasket) lets in outside air that confuses the downstream O2 sensor into reading as if the catalyst isn't working, even when it is.

Compare upstream and downstream O2 sensor activity

Look for: A healthy converter makes the downstream sensor read flat and steady while the upstream sensor swings actively. If the downstream sensor switches nearly as fast as the upstream one, the converter isn't storing oxygen properly and is likely worn out.

Check converter temperature and performance

Look for: A converter outlet noticeably cooler than expected relative to its inlet under load suggests little catalytic reaction is happening inside — supports a genuinely failed converter rather than a false reading.

Hold off on replacing the converter until root causes are ruled out

Look for: If misfires, exhaust leaks, or fuel trim issues caused this code, a new converter will fail again quickly — confirm those are clean first.

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Matching symptoms

Check Engine Light