P0430
Catalyst System Efficiency Below Threshold (Bank 2)
Quick answer: P0430 means catalyst System Efficiency Below Threshold (Bank 2). Fixing the underlying cause typically runs $330 to $3,250 at an independent shop. Drive gently, service soon.
- Severity
- Moderate
- Safe to drive?
- Drive gently, service soon
- Typical repair
- $330 to $3,250
- Most likely cause
- A worn-out catalytic converter on bank 2, common past 100,000 miles (the most likely single-side cause and the expensive one)
What P0430 means
This is the exact same test as P0420, just on bank 2, the cylinder bank that does not contain cylinder 1. You only see P0430 on engines with two banks (V6, V8, and other V-configurations), which is why four-cylinder cars never throw it. The computer compares the oxygen sensors before and after the bank 2 converter and decides that side is no longer cleaning the exhaust well enough. On a V engine it is common to see P0420 and P0430 together, which usually points at a whole-engine cause rather than one dead converter.
Common symptoms
What drivers usually notice with this code.
- Steady check-engine light, often with no change at all in how the car drives
- Failed state emissions or smog test
- A rotten-egg or sulfur smell from the exhaust
- Slightly reduced fuel economy or mildly sluggish acceleration
- Rattling from under the car if the bank 2 converter's internals have broken up
Common causes
Ranked from most to least likely.
- 1A worn-out catalytic converter on bank 2, common past 100,000 miles (the most likely single-side cause and the expensive one)
- 2A failing downstream (post-cat) oxygen sensor on bank 2 reporting bad data
- 3An exhaust leak at a gasket, flex pipe, or weld near the bank 2 converter, letting fresh air skew the readings
- 4An unresolved misfire or a rich condition that cooked the converter (fix that first, or a new converter dies too)
- 5An engine burning oil or coolant, which poisons the catalyst and often takes out both banks at once (this is why P0420 frequently appears alongside it)
- 6A cheap aftermarket converter installed previously that never met spec
Can I keep driving?
Yes, this one is safe to drive with for a while, but it will fail an emissions test and the converter behind it does not get cheaper by waiting.
Severity: Moderate. A flashing check-engine light always means stop, whatever the code says.
Ballpark cost
What P0430 usually costs to fix
A range, not a quote. What you pay depends on your vehicle, your area, and which of the causes above turns out to be the real one.
Typical parts and labor at an independent shop. Dealer rates run higher.
That spread is wide on purpose. P0430 points at a system, not a single part, so the real answer depends on what the diagnosis finds. Use the range to know what to expect. If an estimate comes in higher, it usually means the specific repair is more involved, and it is always fair to ask what is included.
Next steps
What to do next
Treat this exactly like P0420 but confirm which side you are dealing with, because bank 2 converters can sit in a more awkward spot and change the labor. Ask the shop to show you the live data from the bank 2 oxygen sensors and to rule out exhaust leaks and stored misfires before quoting a converter. If both P0420 and P0430 are present, be extra skeptical of a plan to replace two converters: two banks failing at once usually means a shared cause (oil consumption, a rich condition, a bad batch of fuel) that would just ruin the new ones too. A quality aftermarket converter and your federal emissions warranty (often 8 years or 80,000 miles) are both worth asking about here.
Walk in informed
Ask for the diagnosis in writing and which test confirmed it, so you understand exactly what is being fixed. Fixxr shows you what the job typically costs near you, so you can approve the work with confidence.
Sources & further reading
- NHTSA — Check for vehicle safety recalls — look up open recalls for your vehicle by VIN, free
- FTC — Auto repair basics — your consumer rights at the repair shop
- AAA — Car repair and maintenance costs — independent guidance on what repairs should cost
Cost ranges and guidance reviewed July 2026.
Keep exploring
What the repair costs
P0430 FAQ
P0430 questions, answered
Can I drive with a P0430 code?
Yes, this one is safe to drive with for a while, but it will fail an emissions test and the converter behind it does not get cheaper by waiting.What does the P0430 code mean?
This is the exact same test as P0420, just on bank 2, the cylinder bank that does not contain cylinder 1. You only see P0430 on engines with two banks (V6, V8, and other V-configurations), which is why four-cylinder cars never throw it. The computer compares the oxygen sensors before and after the bank 2 converter and decides that side is no longer cleaning the exhaust well enough. On a V engine it is common to see P0420 and P0430 together, which usually points at a whole-engine cause rather than one dead converter.What are the most common causes of a P0430 code?
The most likely causes, roughly in order, are a worn-out catalytic converter on bank 2, common past 100,000 miles (the most likely single-side cause and the expensive one); a failing downstream (post-cat) oxygen sensor on bank 2 reporting bad data; an exhaust leak at a gasket, flex pipe, or weld near the bank 2 converter, letting fresh air skew the readings; an unresolved misfire or a rich condition that cooked the converter (fix that first, or a new converter dies too). Treat this exactly like P0420 but confirm which side you are dealing with, because bank 2 converters can sit in a more awkward spot and change the labor. Ask the shop to show you the live data from the bank 2 oxygen sensors and to rule out exhaust leaks and stored misfires before quoting a converter. If both P0420 and P0430 are present, be extra skeptical of a plan to replace two converters: two banks failing at once usually means a shared cause (oil consumption, a rich condition, a bad batch of fuel) that would just ruin the new ones too. A quality aftermarket converter and your federal emissions warranty (often 8 years or 80,000 miles) are both worth asking about here.How much does it cost to fix a P0430 code?
Fixing the underlying problem behind a P0430 code typically runs $330 to $3,250 at an independent shop, including parts and labor. The exact figure depends on your vehicle and which part turns out to be at fault.
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