P0420 Dodge Charger
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 Dodge Charger 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 Dodge Charger.
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 Dodge Charger.
Common Causes on Dodge Charger
- Catalytic converter degradation from MDS oil consumption on 5.7L/6.4L HEMI (Charger/Challenger)
- Downstream O2 sensor failure from extreme exhaust temperatures during performance driving
- Aftermarket exhaust system with high-flow cats or catless pipes triggering P0420
- Catalyst thermal damage from aggressive driving and repeated high-RPM operation
- Exhaust manifold bolt failure causing pre-catalyst exhaust leak on HEMI V8
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 Dodge Charger
Performance driving significantly reduces catalytic converter lifespan on HEMI engines.