P0431 Code: Catalyst 1 Efficiency Below Threshold (Bank 2)
🟠 Moderate severity · drivable
Drivable, but the converter isn't cleaning exhaust efficiently and may eventually need replacing.
What P0431 means
The first catalytic converter on bank 2 (the side of the engine opposite cylinder 1) is not cleaning exhaust as well as it should. This is the bank 2 version of the well-known P0430 code.
Symptoms
- Check engine light is on
- Reduced fuel economy
- Possible failed emissions test
- Often no noticeable driving symptoms
Common causes
- most common: Failing catalytic converter
- common: Faulty oxygen sensor
- common: Exhaust leak near a sensor
- less common: Engine running rich due to a misfire or fuel issue
How to fix it
| Fix | DIY? | Typical cost |
|---|---|---|
| Test the oxygen sensors and replace any that are faulty | Yes | $60–200 |
| Repair exhaust leaks | Mechanic | $50–200 |
| Replace the catalytic converter | Mechanic | $600–2000 |
Frequently asked questions
Can I drive with a P0431 code?
Yes, but the converter isn't cleaning exhaust efficiently. Get it diagnosed before too long.
What is the most common cause of P0431?
A failing catalytic converter, though a bad oxygen sensor or an exhaust leak can also trigger it.
How much does it cost to fix P0431?
$60–200 for an oxygen sensor, or $600–2000 for a new catalytic converter plus labor.
Related codes
P0430
P0430 Code: Catalyst System Efficiency Below Threshold (Bank 2)
P0420P0420 Code: Catalyst System Efficiency Below Threshold (Bank 1)
P0432P0432 Code: Catalyst 2 Efficiency Below Threshold (Bank 2)
Related guide: How to Reset a Check Engine Light →
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.