P0420 Chevrolet Trax
Catalyst System Efficiency Below Threshold (Bank 1) · Powertrain Code · Medium · Repair: Moderate
What is P0420?
The catalytic converter on bank 1 is not operating efficiently. The downstream O2 sensor readings indicate the catalyst is not converting exhaust gases properly. May need catalyst replacement or could be caused by a failed O2 sensor.
When the Chevrolet Trax triggers code P0420 (catalyst system efficiency below threshold (bank 1)), it typically points to an issue in the powertrain system. Below you'll find the most common causes, symptoms, and repair options specific to the Chevrolet Trax.
This repair is rated moderate, meaning some experience and specialty tools required.
Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your Chevrolet Trax.
Common Causes on Chevrolet Trax
- Close-coupled catalytic converter degradation on 1.2L/1.3L turbo three-cylinder
- Downstream O2 sensor failure from moisture exposure on low-mounted exhaust
- Exhaust manifold gasket leak causing upstream O2 sensor inaccuracy
- Catalyst contamination from excessive oil consumption on turbo engine
- Small displacement engine running rich during cold starts fouling catalyst over time
Symptoms
- Check engine light illuminated steadily
- Reduced fuel economy compared to normal
- Sulfur or rotten egg smell from exhaust
- Failed emissions inspection or smog test
- Slight loss of power at highway speeds
- Rough or uneven exhaust note
Notes for Chevrolet Trax
Three-cylinder engines produce pulsating exhaust flow that stresses catalytic converters differently.