P0430

Catalyst System Efficiency Below Threshold Bank 2

Catalyst / emissions Generic OBD-II Medium

What it means

P0430 means the catalytic converter on bank 2 (the cylinder bank without cylinder #1) isn't cleaning the exhaust as well as it should. The ECM compares the upstream and downstream oxygen sensors and sees the converter falling short. The car still drives normally, but it will fail emissions and the cause should be tracked down.

Medium

Can I keep driving? Yes — the car drives normally, but it will fail emissions and the underlying cause can worsen over time, so get it diagnosed.

Real-world scan data

Seen in

1,829

scans in the past year

Found in

0.3%

of scans

0.5%

of scans that found faults

Appears alongside · share of P0430 scans

P0420in 52.6% of scans

P0300in 10.1% of scans

P0128in 4.9% 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
Failed emissions or smog test
Slightly reduced fuel economy
Rotten-egg (sulfur) smell in some cases

Common causes

Most likely first

Worn-out or failed catalytic converter on bank 2Likely
Faulty downstream (post-catalyst) oxygen sensor giving a bad readingCommon
Exhaust leak near the sensors or a leaking manifold gasketCommon
Upstream problem overloading the converter — a misfire or rich-running conditionLess often
Rarely, a faulty ECM misreading sensor dataLess often

How to diagnose & fix

Work through it in order

Read freeze-frame and check for other codes first — fix any misfire, rich, or O2-sensor codes before condemning the converter.
Inspect the bank 2 exhaust for leaks at the manifold, flanges, and around both O2 sensors.
Compare upstream and downstream O2 sensor waveforms; a downstream sensor that mirrors the upstream one points to a worn converter.
Replace the failed downstream O2 sensor if it tests bad.
If the converter is confirmed dead and no upstream cause remains, replace the bank 2 catalytic converter.

FAQ

Quick answers

Is it safe to drive with P0430?+

Yes, short-term — the engine runs normally. But a failing converter can eventually clog and restrict exhaust, so don't leave it indefinitely, and fix any misfire first.

Can I just clear P0430?+

You can, but it returns after the emissions monitor re-runs unless the converter or its cause is actually repaired.