The 2022 Ford Transit Connect's check engine light with code P0420 indicates the catalytic converter isn't meeting efficiency standards. This affects emissions compliance and may indicate converter or related problems.
Catalyst Efficiency Monitoring
The ECU compares upstream and downstream oxygen sensor signals to determine catalyst effectiveness. When the converter can't adequately treat exhaust, efficiency codes set.
Causes of P0420
Aging Catalytic Converter
Catalytic converters degrade over time. Commercial use with frequent cold starts can accelerate wear.
Oxygen Sensor Problems
Faulty oxygen sensors provide incorrect data to the ECU. A bad downstream sensor can trigger P0420 even with a good converter.
Exhaust Leaks
Leaks between the engine and downstream sensor allow air into the exhaust, affecting sensor readings and converter operation.
Engine Running Conditions
Rich or lean running conditions, misfires, or other engine problems send improper exhaust to the converter, potentially causing P0420.
Proper Diagnosis
P0420 doesn't automatically mean converter replacement. Systematic diagnosis prevents unnecessary parts replacement.