P0421 – Meaning, Causes, Symptoms, & Fixes
Code P0421 Definition Bank 1 Catalytic Converter Efficiency is Below Threshold on Cold Start What Does P0421 Mean? When this code is triggered the ECM (Engine Control Module) has deduced, through programmed rationality, that the Bank 1 Catalytic Converter isn’t warming up sufficiently; therefore, it’s not cleaning up the exhaust as well as it is...