P0430 – Catalyst System Efficiency Below Threshold (Bank 2)
Similar to P0420 but for Bank 2, indicating that the catalytic converter on the second bank is not cleaning up exhaust gases as expected.
Plain‑English Explanation
The ECU compares oxygen sensor signals before and after the catalytic converter. If the downstream sensor on Bank 2 starts to behave too much like the upstream sensor, it suggests the catalyst is no longer storing and releasing oxygen effectively. When this behaviour persists, P0430 is logged.
Common Symptoms
- Check engine light on.
- Often no noticeable driveability change.
- May be accompanied by other mixture or misfire codes.
- In some cases, slight loss of performance or fuel economy.
Typical Causes
- Ageing or damaged catalytic converter on Bank 2.
- Persistent misfires or rich/lean running that have overheated the catalyst.
- Exhaust leaks near the Bank 2 sensors.
- Faulty Bank 2 oxygen sensors or wiring.
What To Check First
- Check for stored or history misfire or fuel trim codes that might have damaged the catalyst.
- Inspect the exhaust system on Bank 2 for leaks before and near the catalyst.
- Use live data to compare upstream and downstream O2 sensor behaviour on both banks.
- If other issues are fixed and P0430 returns, the Bank 2 catalyst may need replacement.