What are the common causes of P0430?

Failing catalytic converter on bank 2. Faulty bank 2 oxygen sensors. Exhaust leak before the bank 2 downstream sensor. Bank 2 engine misfires over-fueling the converter. Damaged exhaust system components.

Compare bank 1 and bank 2 O2 sensor activity on an OBD-II scanner. Smoke test the exhaust for leaks on the bank 2 side. Verify no misfires exist that could damage the converter. Monitor fuel trims for coolant or oil contamination. Replace the bank 2 converter if efficiency test fails.

P0430

Catalyst System Efficiency Below Threshold (Bank 2)

System: Auxiliary emission controls (P code)
Lamp: Check Engine Light
Category: Powertrain - Auxiliary Emissions Controls

What it means

P0430 means Catalyst System Efficiency Below Threshold (Bank 2).

Check these first

Failing catalytic converter on bank 2
Faulty bank 2 oxygen sensors
Exhaust leak before the bank 2 downstream sensor
Bank 2 engine misfires over-fueling the converter
Damaged exhaust system components

What to do next

Compare bank 1 and bank 2 O2 sensor activity on an OBD-II scanner
Smoke test the exhaust for leaks on the bank 2 side
Verify no misfires exist that could damage the converter
Monitor fuel trims for coolant or oil contamination
Replace the bank 2 converter if efficiency test fails

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Updated

Generic SAE J2012 definition. Last updated 2026-08-30.