P0422 Code: Catalyst 2 Efficiency Below Threshold (Bank 1)
🟠 Moderate severity · drivable
Drivable, but the second catalytic converter isn't cleaning exhaust efficiently and may need replacing.
What P0422 means
The second catalytic converter on bank 1 isn't cleaning the exhaust as well as it should. This code is like P0420 but for the second converter, so it usually means that converter has worn out or an oxygen sensor is lying to the computer.
Symptoms
- Check engine light is on
- Reduced fuel economy
- Possible failed emissions test
- Often no noticeable driving symptoms
Common causes
- most common: Failing second catalytic converter
- common: Faulty downstream oxygen sensor
- common: Exhaust leak near the converter or sensor
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 second catalytic converter | Mechanic | $600–2000 |
Frequently asked questions
Can I drive with a P0422 code?
Yes, but the second converter isn't cleaning exhaust efficiently. Get it diagnosed before your next emissions test.
What is the most common cause of P0422?
A failing second catalytic converter, though a bad oxygen sensor or exhaust leak can also trigger it.
How much does it cost to fix a P0422?
$60–$200 for an O2 sensor, or $600–$2,000 for a new catalytic converter.
Related codes
P0420
P0420 Code: Catalyst System Efficiency Below Threshold (Bank 1)
P0432P0432 Code: Catalyst 2 Efficiency Below Threshold (Bank 2)
P0136P0136 Code: O2 Sensor Circuit Malfunction (Bank 1 Sensor 2)
Updated 2026-08. This page is informational and not a substitute for professional diagnosis.