Honda P0420 — Meaning, Causes & Fixes
Guidance for the P0420 code on popular Honda vehicles like the Civic, Accord, and CR-V.
Common Causes for a P0420 on a Honda
On many Honda models, a P0420 code is very frequently caused by a degraded catalytic converter. However, other issues are still possible.
- Failing Catalytic Converter: The most common cause on high-mileage Hondas.
- Faulty O2 Sensors: Honda O2 sensors can become lazy over time, leading to inaccurate readings.
- Valve Adjustments: On some older models, incorrect valve clearance can affect engine combustion and lead to a P0420 code.