P0430 Catalyst system efficiency below threshold (bank 2)
What P0430 means
On V6, V8 and other engines with two exhaust banks, each bank has its own catalytic converter. P0430 means the converter on bank 2 (the side without cylinder 1) is no longer storing oxygen effectively, judged by comparing the oxygen sensors before and after it. The engine runs normally, but emissions are higher.
P0430 is a generic SAE J2012 code: it means the same on every make. The exact cause still depends on the car, so read the freeze-frame data before replacing parts.
At a glance
- Severity
- Medium
- Typical repair cost
- 150–900 €
- Workshop time
- 1.5–5 h
- Repair difficulty
- Hard
- DIY possible
- No
- Check engine light
- Yes
- Affects emissions test
- Yes
Parts and labour at an independent workshop in Europe. Main dealers charge more; the cause decides the bill, not the code.
Symptoms
- Check engine light on
- Usually no change in driving
- Rotten-egg smell from the exhaust
- Technical inspection failure for emissions
Common causes
- Worn-out or damaged bank 2 catalytic converter
- Faulty or slow bank 2 downstream oxygen sensor
- Exhaust leak on bank 2 near the sensors
- Past misfires or rich running that overheated the catalyst
- Oil or coolant consumption contaminating the catalyst
Can I keep driving with P0430?
You can keep driving. Have it diagnosed within one or two weeks, and fix any misfire codes first so a new catalyst is not damaged.
What to check first
- Fix any misfire, fuel trim or oxygen sensor codes first
- Check bank 2 exhaust for leaks before and around the rear oxygen sensor
- Compare bank 2 front and rear oxygen sensor signals with a warm engine
- Replace the rear sensor if it is faulty; replace the catalyst only once a weak catalyst is confirmed
Related codes
- P0431 Warm-up catalyst efficiency below threshold (bank 2)
- P043E EVAP leak detection reference orifice low flow
- P043F EVAP leak detection reference orifice high flow
- P0421 Warm-up catalyst efficiency below threshold (bank 1)
- P0440 Evaporative emission (EVAP) system malfunction
- P0420 Catalyst system efficiency below threshold (bank 1)
- P0441 EVAP system incorrect purge flow
- P0442 EVAP system small leak detected
Data: TORKO fault-code catalogue, built on OBDex (CC0-1.0) and reviewed against workshop practice. Informational only — it does not replace a diagnosis by a mechanic.
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