P0430 on Hyundai: How to Diagnose & Fix
Catalyst System Efficiency Below Threshold (Bank 2)
1 Hyundai model · 1 documented issue · $500-$2,500 repair
P0430 on Hyundai by model: symptoms, diagnosis and fix
P0430 (Catalyst Efficiency Below Threshold, Bank 2) applies only to the V6 Sonata, which has two catalyst banks. On the 2006-2010 Sonata 3.3L Lambda V6 the bank 2 warm-up catalytic converter degrades so the downstream O2 sensor tracks the upstream sensor too closely, indicating the cat can no longer store/convert oxygen efficiently. Age, high mileage, or upstream causes (an exhaust leak or a lazy/failing O2 sensor) accelerate it.
Common Symptoms
- Check engine light
- Failed emissions/smog test
- Slight loss of fuel economy
- Rotten-egg exhaust smell
- Usually no drivability change
How to Fix
Verify there is no exhaust leak and that both bank 2 O2 sensors are healthy (a failing rear sensor can mimic P0430). If the converter is confirmed inefficient, replace the bank 2 catalytic converter — replacing the O2 sensor alone sometimes clears it but usually the cat must be replaced.
Sources for this issue (3)
P0430 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0430 mean on a Hyundai?
P0430 stands for "Catalyst System Efficiency Below Threshold (Bank 2)." This code means the catalytic converter on Bank 2 (the side of the engine that does not contain cylinder #1) is not reducing emissions as effectively as it should. The computer compares the readings of the oxygen sensors before and after the converter; if the downstream sensor's signal starts mirroring the upstream one, it indicates the converter is no longer storing and processing oxygen properly. This usually points to a worn-out or damaged catalytic converter, but it can also be caused by faulty sensors or upstream engine problems that have poisoned the converter. The car will generally still run, but it will fail an emissions test. On Hyundai it is documented across 1 model: Sonata.
What are the most common causes of P0430?
The most common causes of P0430 are: Worn-out or failed catalytic converter (Bank 2), Faulty downstream (post-cat) oxygen sensor, Faulty upstream oxygen sensor giving bad data, Exhaust leak near the converter or sensors, Engine misfire or oil/coolant burning that damaged the catalyst, Running too rich or too lean over time, Aftermarket or non-compliant catalytic converter. The specific cause varies by vehicle.
How much does it cost to fix P0430 on a Hyundai?
Published repair estimates on Hyundai range from $500 to $2,500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0430 on a different make?
View P0430 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.