P0420 Code Catalytic Converter Efficiency Below Threshold – Fixes & Solutions
What Does the P0420 Code Mean? The P0420 code stands for: “Catalyst System Efficiency Below Threshold (Bank 1).” This means that the catalyst system efficiency is below the expected threshold, typically indicating that the converter is not functioning properly. The engine control unit (ECU) monitors the oxygen sensors before and after the catalytic converter. If…