Bank 2 counterpart to P0420: the bank 2 catalytic converter is calculated to be converting inefficiently. Same diagnostic approach - confirm the downstream O2 sensor and rule out upstream faults before replacing the converter.
SYMPTOMS
- Check-engine light
- No obvious drivability change
- Emissions failure
LIKELY CAUSES
- Aged/degraded catalytic converter (bank 2)
- Lazy downstream O2 sensor
- Prior misfire / oil contamination
- Exhaust leak
DIAGNOSIS STEPS
- Compare bank 2 upstream vs downstream O2 signals
- Rule out misfire and mixture codes first
- Check for exhaust leaks
- Test the downstream sensor before replacing the cat
RELATED PARTS
- Catalytic converter (Bank 2)
- Downstream O2 sensor