P0431 Code: Warm-Up Catalyst (Bank 2) — Causes & Fix
P0431 means the warm-up catalytic converter efficiency on bank 2 is below threshold (the bank not containing cylinder 1 on V-engines).
- Applies to
- All OBD-II vehicles (any make or model)
- Est. repair cost
- $100 – $1,500
- Time to fix
- 30 minutes – 2 hours
What it means
Causes include an aged converter, a lazy O2 sensor, or an exhaust leak on bank 2. P0431 is a generic OBD-II powertrain code defined in the SAE J2012 standard, so it applies to virtually any 1996-or-newer petrol car or light truck regardless of make. Fix the underlying fault, then clear the code with an OBD-II scan tool — it will return if the problem isn't resolved.
Symptoms
- Check engine light on
- Slight economy drop
- Possible smell; failed emissions
How to fix it
- 1
Check bank 2 O2 sensors/leaks
1. Rule out a lazy sensor or exhaust leak on bank 2.
- 2
Replace the converter
1. Confirm the fault, then replace the bank 2 converter and clear the code.
Frequently asked questions
Where is bank 2?
On a V6/V8, bank 2 is the side without cylinder 1. P0431 is its warm-up (close-coupled) converter.
Last updated July 19, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.