P0422 Code: Catalyst Efficiency (Bank 1) — Causes & Fix
P0422 means the main catalytic converter efficiency on bank 1 is below threshold — the converter isn't cleaning the exhaust well enough.
- 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. P0422 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
- Rotten-egg smell; failed emissions
How to fix it
- 1
Verify sensors and leaks first
1. Rule out a lazy O2 sensor or exhaust leak.
- 2
Replace the converter
1. Confirm the converter is the fault. 2. Replace with an OEM-grade unit, then clear the code.
Frequently asked questions
Is P0422 like P0420?
Yes — both are bank 1 catalyst-efficiency codes. Confirm the O2 sensors and check for leaks before replacing the converter.
Last updated July 19, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.