Catalytic Converter Education Archive

Why Converters Fail

Most catalytic converters fail due to engine related problems. Replacing the catalytic converter without fixing the cause of the failure may lead to another ruined converter.

OBD II trouble code P0420

Code P0420 indicates that the “catalyst system efficiency is below threshold bank 1 or 2”. In other words, the vehicle’s oxygen sensors downstream noticed that the converter is not working as efficiently as it should be. Code P0420 can occur for a variety of reasons other than converter failure or malfunction. It is important to properly diagnose and identify any problem or problems before installing a new catalytic converter.

Common causes of failure:

Most catalytic converter failures are caused by conditions or events other than converter malfunction:

• Melted or rattling brick: usually caused by raw fuel entering the converter and superheating the substrate.
• Contaminated brick: oil, antifreeze, or fuel additives coat and plug up the substrate, preventing the converter’s chemical reaction from taking place.
• Road damage: caused from road debris striking the converter and causing internal damage.