Cadillac DeVille 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 Cadillac DeVille 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 Cadillac DeVille’s catalytic converter is not scrubbing pollutants efficiently … Read more