P0430Powertrain
Powertrain · SAE
Catalyst System Efficiency Below Threshold (Bank 2)
Meaning
The downstream oxygen sensor on bank 2 indicates that the catalytic converter is not reducing emissions effectively enough. The converter no longer stores oxygen as it should.
Common causes
- Aged or damaged bank 2 catalytic converter
- Faulty or slow downstream oxygen sensor
- Exhaust leak upstream of the catalyst
- Misfire or incorrect mixture damaging the catalyst
- Oil or coolant contamination poisoning the catalyst
Symptoms
- Check-engine light on
- Usually no noticeable drivability symptoms
- Possible emissions-test failure
- Slight rise in fuel consumption in the worst cases
- Possibly a stronger exhaust smell
Severity
Moderate: an emissions issue, not a risk of immediate mechanical damage.
What to do
- Compare the upstream and downstream oxygen sensor signals on bank 2
- Check for exhaust leaks ahead of the catalytic converter
- Rule out misfire or incorrect mixture that could skew the diagnosis
- Replace the catalyst only after ruling out the sensor and upstream causes