P0430
P0430 Check Engine Code
Catalyst System Efficiency (Bank 2)
Same catalyst-efficiency story as P0420, but on bank 2 — the side of a V engine that does not include cylinder 1. P0430 means that bank's catalytic converter is not cleaning exhaust well enough for the oxygen sensors to pass their monitor. A worn cat, a slow O2 sensor, or an exhaust leak can all set it. Verify engine health and sensors on that bank before assuming the converter failed — otherwise you buy hardware the real fault will destroy again.
Symptoms
- Check engine light with P0430 — may appear alone or with P0420
- Emissions test failure on bank 2 monitors
- History of misfire on bank 2 cylinders
- Exhaust or header work on one bank recently
- Often no noticeable driveability symptom until engine faults are present
Can I keep driving with a P0430 code?
Similar to P0420 — if it runs normally without misfire, you can usually drive to diagnosis. Emissions compliance is the pressing issue.
Fix active misfire on bank 2 before replacing a converter.
Rattling exhaust or power loss needs inspection — not just a code clear.
Common causes
- Worn catalytic converter on bank 2
- Downstream O2 sensor on bank 2 slow or reading wrong
- Exhaust leak affecting bank 2 sensor readings
- Bank 2 misfire or rich running that damaged the catalyst
- P0420 and P0430 together — both converters aged, or a systemic engine issue
Often sounds like
- P0420 bank 1 — same diagnosis path, different bank
- Bank 2 misfire codes P0302, P0304, P0306, P0308 — fix ignition before blaming the cat
- O2 sensor heater codes on bank 2
If you wait
- Emissions failure at registration
- Repeat converter damage if bank 2 misfire continues
- Replacing one bank while the other fails shortly after on high-mileage V engines
How we check it
- 1 Same verification path as P0420 — misfire, leaks, O2 response, then converter
- 2 Compare both banks when only one side sets efficiency codes
What happens next when you bring it in?
- 1 Call with engine size (V6 or V8) and whether P0420 is also stored.
- 2 We scan both banks, inspect the exhaust, and test sensors before quoting bank 2 converter work.
Questions we get a lot
- What is the difference between P0420 and P0430?
- P0420 is catalyst efficiency on bank 1. P0430 is bank 2. Bank 1 is the side of the engine that has cylinder 1. Bank 2 is the opposite side on a V engine. Each bank has its own converter and downstream oxygen sensor. Diagnosis is the same — check engine health and sensors before replacing hardware.
- How do you diagnose P0430?
- Same path as P0420: misfire counters, exhaust leaks, O2 sensor tests, then converter condition — bank-specific, not a generic cat quote.
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