P0431

Catalyst 1 Efficiency Below Threshold Bank 2

Q: Is it safe to drive with P0431?

Yes. The car drives normally; this code means the bank 2 converter isn't cleaning the exhaust well enough, so fix it to pass emissions.

Q: Can I just clear P0431?

It returns after the catalyst monitor re-runs unless the converter or the underlying cause is repaired.

Catalyst / emissions Generic OBD-II Medium

What it means

P0431 means the catalytic converter on bank 2 isn't cleaning the exhaust as efficiently as the ECM expects, based on the upstream and downstream oxygen sensor readings. The engine still runs normally. The usual cause is an aged converter, but a faulty downstream O2 sensor or an upstream misfire can also trigger it.

Medium

Can I keep driving? Safe to keep driving — the engine runs normally; this is an emissions-efficiency fault, so fix it to pass inspection and stop the light.

Real-world scan data

Seen in

scans in the past year

Found in

<0.1%

of scans

Figures reflect only diagnostic scans recorded through our own apps and tools. Cars are typically scanned because a symptom or warning light prompted it, so these counts describe our scan records — not the incidence of faults in any model, and not the quality, reliability, or safety of any vehicle. No comparison between manufacturers or models is implied. All trademarks belong to their respective owners; no affiliation or endorsement is implied.

Common symptoms

What you'll notice

Check-engine light on (often the only sign)
May fail an emissions/smog test
Occasionally a faint sulfur or rotten-egg smell from the exhaust
Slightly worse fuel economy in some cases

Common causes

Most likely first

Aged or failed catalytic converter on bank 2 (most common)Likely
Faulty bank 2 downstream oxygen sensor giving a false efficiency readCommon
Exhaust leak near the converter or the rear O2 sensorCommon
An upstream misfire or rich condition that has damaged the converterLess often

How to diagnose & fix

Work through it in order

Confirm there are no misfire, fuel-trim, or O2-sensor codes first — fix those before condemning the converter.
Compare the bank 2 upstream and downstream O2 sensor traces live; a downstream sensor mirroring the upstream points to a worn converter.
Inspect the exhaust for leaks near the converter and rear sensor.
Replace the bank 2 downstream O2 sensor if it's proven faulty; otherwise replace the bank 2 catalytic converter.
Clear the code and let the catalyst monitor re-run to confirm the repair.

P0431 by make

Based on commonly reported failure patterns across owner and repair communities, not on our scan data.

Ford

On Ford V6 and V8 models, bank 2 converter wear is commonly reported as the engine ages. Fix any misfires first.

Honda

On Honda V6 models, a slow bank 2 air-fuel sensor can mimic a worn converter. Have the sensor readings checked first.

Toyota

On Toyota V6 models, bank 2 converter wear shows up as engines age. Check the exhaust for leaks and the sensors before replacing it.

FAQ

Quick answers

Is it safe to drive with P0431?+

Yes. The car drives normally; this code means the bank 2 converter isn't cleaning the exhaust well enough, so fix it to pass emissions.

Can I just clear P0431?+