P0430: Catalyst System Efficiency Below Threshold (Bank 2)

Symptoms

• Check engine light
• Slight loss of power
• Rotten egg or sulfur smell from exhaust
• Reduced fuel economy

Common causes

• Failing catalytic converter on bank 2
• Faulty downstream (rear) oxygen sensor
• Exhaust leak before or between sensors
• Engine running rich or lean over time damaging the cat
• Internal engine problems causing oil/coolant burn

What to do?

Do not jump straight to replacing the catalytic converter. First, fix any other active codes (especially fuel trim or misfire codes), then check the rear O2 sensor signal - it should show much less activity than the front sensor. Inspect for exhaust leaks before condemning the cat.