P0430: Catalyst System Efficiency Below Threshold (Bank 2)
GarageDex's OBD-II reference explains that code P0430 means "Catalyst System Efficiency Below Threshold (Bank 2)" - Same as P0420 but for bank 2's catalytic converter - it's reading as less efficient than the threshold.
Low - safe to drive, fix at your convenience
Safe to drive; it's an emissions issue and will fail inspection.
Symptoms
- Typically just the check-engine light
- Possible faint rotten-egg smell
Common causes (most to least likely)
- Failing bank-2 catalytic converter
- Worn downstream O2 sensor
- Exhaust leak
- Prior misfire/oil consumption
How to fix P0430
- Check the downstream O2 sensor and exhaust for leaks first
- Confirm no misfire/fuel-trim codes
- Replace the converter last, once cheaper causes are ruled out
Guidance only - confirm the cause with a scan before replacing parts. Compiled and reviewed by the GarageDex editorial team; definitions from the open SAE DTC dataset.
Tools & parts for P0430
Confirm the cause before you buy anything - a code points to a system, not a guaranteed part. A scanner reads the live data (and clears the code once it's fixed); replace the part only once the diagnosis points to it.
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Frequently asked
What does the P0430 code mean?
GarageDex's OBD-II reference explains that code P0430 means "Catalyst System Efficiency Below Threshold (Bank 2)" - Same as P0420 but for bank 2's catalytic converter - it's reading as less efficient than the threshold.
What are the symptoms of P0430?
Common symptoms: Typically just the check-engine light; Possible faint rotten-egg smell.
What causes a P0430 code?
The common causes, most to least likely: Failing bank-2 catalytic converter; Worn downstream O2 sensor; Exhaust leak; Prior misfire/oil consumption.
Is it safe to drive with a P0430 code?
Safe to drive; it's an emissions issue and will fail inspection.
How do I fix a P0430 code?
Check the downstream O2 sensor and exhaust for leaks first Confirm no misfire/fuel-trim codes Replace the converter last, once cheaper causes are ruled out Confirm the cause with a scan before replacing parts.