The Bank 1 main catalyst is below its efficiency threshold.
SYMPTOMS
- Check-engine light
- Failed emissions
LIKELY CAUSES
- Aged or failed catalyst
- Exhaust leak
- Faulty O2 sensor
DIAGNOSIS STEPS
- Confirm no misfire/lean codes first
- Compare front vs rear O2 traces
- Inspect for exhaust leaks
RELATED PARTS
- Catalytic converter
- O2 sensors