P0430 — Catalyst efficiency below threshold (Bank 2)
Same idea as P0420, but for bank 2 — the other cylinder bank on a V-engine (or the labeled bank on some layouts).
What it means in plain English
P0430 is the bank-2 counterpart of P0420: catalyst efficiency below threshold on bank 2. On inline engines you may only see P0420; on V6/V8 engines both banks can set codes independently. Diagnosis still starts with sensors, exhaust leaks, and engine health — not “replace both converters.”
Common causes
- Worn catalytic converter on bank 2
- Bank-2 oxygen sensor problems
- Exhaust leak on that bank
- Bank-specific misfire or fueling issues
What you can safely check
- Pull all codes; note if P0420 appears with P0430 (both banks) vs bank 2 alone.
- Write down symptoms: smell, power loss, rattling exhaust.
- Share freeze-frame (engine temp, load, fuel trims) with the shop.
Pull the code yourself (disclosed)
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A reusable Bluetooth OBD-II scanner lets you read the code and freeze-frame data before authorizing “mystery” diagnostics. One option: BlueDriver Bluetooth Pro OBD-II scan tool (BlueDriver/Levanta affiliate). Any capable OBD-II reader is fine — this is not required to use Fair Auto Shops.
When to go to a shop
Seek diagnosis when the light is on for emissions readiness, drivability suffers, or both bank codes appear. Ask which tests isolate bank 2 before authorizing dual converters.
Typical related repair costs (U.S. national averages)
These are related repairs shops may find after diagnosis — not a guaranteed bill for every P0430. Ranges exclude taxes, fees, diagnostics, and your location.
- $440–$523 national average for oxygen sensor replacement (RepairPal; estimates last updated September 3, 2026; excludes taxes/fees and location; source). Labor $93–$136; parts $347–$387.
- $2,280–$2,480 national average for catalytic converter replacement (RepairPal; estimates last updated September 3, 2026; excludes taxes/fees and location; source). Labor $236–$347; parts $2,044–$2,133.
Bank-2 converter labor can differ by vehicle packaging; quotes should name which converter and which sensors were tested.
Related cost guides: Catalytic Converter · Oxygen Sensor
Questions to ask before you authorize work
Use questions before you authorize a repair and how to read a repair estimate. Watch for patterns in spotting upselling.
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FAQ
Is P0430 worse than P0420?
Neither is inherently “worse” — both mean a bank failed the efficiency monitor. Severity depends on drivability and whether the converter is clogged or just inefficient.
More check-engine codes
P0420 · P0300 · P0301 · P0171 · P0174 · P0455 · P0456 · P0442 · P0446 · P0128 · P0401 · P0133 · P0113 · P0506 · P0507 · P0700 · P0741 · P0011 · P0325 · P0340 · P0335 · P0101 · P0299 · P0135 · P0440 · P0441 · P0010 · P0500 · P0121
Hub: How to read a check-engine code · Repair cost guides · Affiliate disclosure