The 2022 Chevrolet Colorado's check engine light with P0420 indicates reduced catalytic converter efficiency. Systematic diagnosis determines whether the converter or related components need attention.
Catalyst Efficiency Monitoring
The ECU compares upstream and downstream oxygen sensor signals to assess converter health. A healthy converter significantly changes exhaust composition; a failing one passes exhaust relatively unchanged.
Causes of P0420
Catalytic Converter Degradation
Converters degrade over time from normal use. Truck use patterns with varying loads can affect converter longevity.
Oxygen Sensor Issues
Faulty oxygen sensors provide incorrect data. A bad downstream sensor can trigger P0420 with a functioning converter.
Exhaust Leaks
Leaks allowing air into the exhaust affect sensor readings and converter operation.
Engine Running Problems
Misfires or rich/lean conditions send improper exhaust to the converter, potentially triggering efficiency codes.
Diagnosis Importance
Don't automatically replace the converter based on P0420. Proper diagnosis prevents unnecessary expense.