P0430: Catalyst System Efficiency Below Threshold (Bank 2)
Key takeaways
- P0430 is the bank 2 version of P0420: the computer thinks the converter on the side without cylinder 1 is no longer storing enough oxygen.
- It is usually safe to drive for now, but a flashing check engine light or a misfire code means stop and fix that first.
- Exhaust leaks, misfires and a tired downstream oxygen sensor set P0430 often enough that a converter should be the last thing replaced, not the first.
- Honda and Ford have both issued bulletins for P0430, including software updates and high-sulfur fuel notes, so ask a dealer to check before you buy parts.
- Fixes run from about $150 for an exhaust leak to $1,000-$2,500 for an aftermarket converter.
What P0430 means
The catalytic converter on the second side of your engine isn’t cleaning the exhaust as well as the computer expects. The scanner name is “Catalyst System Efficiency Below Threshold (Bank 2)”. Bank 2 is the side of a V6 or V8 that does not contain cylinder 1. The computer compares the oxygen sensor in front of that converter with the one behind it. A healthy converter stores oxygen, so the rear sensor reads steady. When the rear sensor starts to switch up and down like the front one, the converter’s efficiency has dropped below the threshold and P0430 sets.
It is the twin of P0420, which runs the same test on bank 1.
Is it safe to drive?
Yes, for now. P0430 on its own does not affect how the engine runs, and most people notice nothing but the light. Plan the repair within a few weeks, because the thing that hurt the converter is usually still happening.
The answer changes if the check engine light starts flashing, or if you also have a misfire code. Unburned fuel from a misfire overheats the converter, so a flashing light means slow down and get off the road. A rattle from under the car or a strong rotten-egg smell also means get it looked at soon.
Causes, ranked
| Cause | How you confirm it | Typical cost (US independent shop, 2026) |
|---|---|---|
| Exhaust leak ahead of the rear bank 2 sensor | Ticking at cold start, soot at a joint, smoke test | $150–$600 |
| Misfire or rich running on bank 2 | Misfire counters, fuel trims, P0300-family codes | $150–$800 |
| Software needs an update | Dealer checks bulletins for your VIN | $0–$200 |
| Slow or failed downstream O2 sensor (bank 2 sensor 2) | Live data: sensor stuck or lazy, P0158 often stored too | $150–$400 |
| Worn or damaged bank 2 converter | Rear sensor mirrors front sensor after the above are ruled out | $1,000–$2,500 |
Aftermarket direct-fit converters sit at the low end of the last row. OEM and California-legal converters can cost more.
What to check first
- Read all stored codes. Misfire, fuel trim or O2 sensor codes get fixed before anything touches the converter.
- Look and listen for exhaust leaks between the engine and the rear bank 2 sensor. Outside air leaking in can fool the rear sensor.
- Ask a dealer to check for bulletins. Honda has a service bulletin for 2017–2019 Pilot with P0430 without a software update, plus a related Odyssey bulletin on PCM software and injectors. Ford has several bulletins for trucks and SUVs, including 2020–2021 Expedition and 2022–2023 F-150 hybrid, that link P0420/P0430 to high sulfur fuel.
- Check the rear bank 2 sensor on live data at a steady 2,500 rpm.
- Clear it and drive. If the converter is marginal, the code will come back within a week or two of mixed driving. That tells you the test is real.
What it costs
The cheap outcome is an exhaust leak or a software update, somewhere from free to about $600. The common outcome is fixing a misfire or a sensor for $150–$800. The expensive outcome is a new bank 2 converter at $1,000–$2,500. Paying $100–$200 for a proper diagnosis first is how you avoid buying a converter that the next misfire would ruin again. If you want a second opinion on your freeze-frame data, ask our AI mechanic.
Related codes
P0430 often shows up alongside P0420 when the cause affects the whole engine. It also appears with misfire codes or bank 2 oxygen sensor codes like P0158. A rotten-egg smell together with P0430 is covered in car smells like rotten eggs. If the car feels normal, see check engine light on but car runs fine.
What owners report to NHTSA
124 complaints filed with NHTSA mention P0430, 107 of them since 2015, across 46 different models. The component owners most often filed it under: engine.
Most-reported models
| Vehicle | Complaints | Model years reported |
|---|---|---|
| HONDA PILOT | 42 | 2016, 2017, 2018, 2019, 2020 |
| FORD F-150 | 14 | 2011, 2012, 2013, 2018, 2019 |
| HONDA ODYSSEY | 7 | 2002, 2018, 2019 |
| FORD EXPLORER | 4 | 2015, 2018, 2019 |
| MERCURY MOUNTAINEER | 3 | 1998 |
| FORD TAURUS | 3 | 2004, 2014 |
| DODGE DURANGO | 3 | 2005, 2007, 2014 |
| ACURA MDX | 3 | 2016, 2018 |
| LINCOLN MKX | 3 | 2016, 2018 |
Manufacturer service bulletins that name P0430
135 technical service bulletins and manufacturer communications filed with NHTSA mention P0430, from 16 makes. A bulletin means the manufacturer has documented a known cause or a fix procedure for that model. Examples:
- FORD F-150 (2022, 2023), bulletin 10244800: Some 2022-2023 F-150 hybrid vehicles equipped with a 3.5L PowerBoost engine may exhibit an illuminated MIL with diagnostic trouble codes (DTCs) P0420 and/or P0430 stored in the powertrain control module (PCM). This may b…
- DODGE CHALLENGER (2023), bulletin 11005019: Spark Plug Re-Gap to Resolve Misfire Symptoms Customers must experience a Malfunction Indicator Lamp (MIL) illumination and the vehicle must exhibit/set one or more of the following Diagnostic Trouble Codes (DTCs): P0300…
- FORD EXPEDITION (2020, 2021), bulletin 10203646: Some 2020-2021 Expedition/Navigator vehicles may exhibit an illuminated malfunction indicator lamp (MIL) with diagnostic trouble codes (DTCs) P0420 and/or P0430 stored in the powertrain control module (PCM). This may be …
- LINCOLN NAVIGATOR (2020, 2021), bulletin 10203646: Some 2020-2021 Expedition/Navigator vehicles may exhibit an illuminated malfunction indicator lamp (MIL) with diagnostic trouble codes (DTCs) P0420 and/or P0430 stored in the powertrain control module (PCM). This may be …
- FORD EXPLORER POLICE INTERCEPT (2020), bulletin 11002862: 2020 Model Year Explorer and Explorer Police Utility Equipped with a 3.3L Engine Replace Catalytic Converters If Failed and Inspect Wire Harness In some of the affected vehicles, one or both of the catalytic converters m…
- FORD POLICE INTERCEPTOR SEDAN (2016, 2017, 2018, 2019), bulletin 10169812: Some 2016-2019 Police Interceptor Sedan vehicles equipped with a 3.7L twin independent variable camshaft timing (Ti-VCT) engine may exhibit an illuminated malfunction indicator lamp (MIL) with diagnostic trouble codes (D…
Sources: NHTSA Office of Defects Investigation complaint database and manufacturer communications file, snapshots September 2026. A complaint or bulletin that mentions a code is a report about that vehicle, not a statement that the code has one cause.
Frequently asked questions
What is the difference between P0420 and P0430?
Same test, different side of the engine. P0420 is bank 1, the side with cylinder 1; P0430 is bank 2, the opposite bank on a V6 or V8. If you have both, look for something that affects the whole engine, like a misfire, a rich condition or a software issue.
Can I just replace the bank 2 oxygen sensor?
Only if testing shows the downstream sensor is slow or stuck. A healthy sensor that correctly reports a worn converter will set the code again within a few drive cycles, and you will have spent $150-$400 for nothing.
Will a P0430 fail an emissions test?
In most states that test by plugging into the OBD port, a stored code with the check engine light on is a fail. Clearing the code right before the test usually does not work either, because the readiness monitors will show as incomplete.
Do catalytic converter cleaners fix P0430?
Sometimes the light stays off for a while after a bottle of cleaner and a long highway drive, especially if the converter was only mildly coated. A converter that is melted, cracked or poisoned by oil or coolant will not come back.
References
- NHTSA Office of Defects Investigation — complaint flat files (snapshot 2026-09-23)
- NHTSA — manufacturer communications / technical service bulletin flat files
- 13 CCR 1968.2 — California OBD II requirements, catalyst monitoring (e)(1), Cornell LII
- 40 CFR §86.1806-17 — Onboard diagnostics (EPA rule for light-duty vehicles, Cornell LII)