Mazda 3 P0421 Code: Meaning, Causes, How to Fix
P0421 is a relatively rare OBDII trouble code. It’s generic, which means it has the same definition for the Mazda 3 as it would any other vehicle. It is technically defined as “Warm Up Catalyst Efficiency → Below Threshold (Bank 1)”. In layman’s terms, it indicates that your Mazda 3’s catalytic converter is not scrubbing pollutants efficiently … Read more