Catalytic Converter

📖 YOUCANIC Automotive Glossary

The catalytic converter is the primary emissions reduction device in the exhaust system, using precious metal catalysts (platinum, palladium, rhodium) on a ceramic or metallic substrate to convert harmful exhaust pollutants — hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) — into less harmful water (H2O), carbon dioxide (CO2), and nitrogen (N2). The catalyst operates at 500-1600F during normal operation and requires stoichiometric fuel control to function efficiently across all three conversions simultaneously (hence the term three-way catalyst).

Catalytic converter failure triggers P0420/P0430 (Efficiency Below Threshold). Causes include age/mileage degradation, thermal damage from misfires (unburned fuel ignites inside the converter), oil or coolant contamination, physical impact, and lead poisoning. Converter theft is extremely common due to the precious metal content. Replacement converters must meet EPA/CARB requirements — in CARB states, only CARB-compliant converters with an Executive Order number are legal. The YOUCANIC UCAN-II Mode $06 data shows catalyst efficiency measurements relative to thresholds.