P0420
Catalyst System Efficiency Below Threshold Bank 1
Generic code
Auxiliary Emissions Control
Medium severity
Moderate repair
Free on OBD DashX
Want real-world data on P0420?
See which problems come with P0420, how often it shows up in other vehicles, and how to fix it — step by step.
- Real-world fix data
- How often it happens
- Step-by-step repairs
What P0420 means
- The fault code P0420 indicates that there is an issue with the catalyst system in bank 1, which could be causing the engine to perform poorly or not start at all.
Possible symptoms
- Illuminated check engine light
- Poor engine performance
- Reduced power or acceleration
- Higher emissions levels
Possible causes
- Faulty catalytic converter
- Oxygen sensor malfunction
- Exhaust leaks
- Fuel system problems
- Ignition system problems
- Engine mechanical problems
Related parts
- Catalytic Converter: A catalytic converter is a device that converts toxic gases and pollutants to less harmful pollutants. Problems lead to harmful emissions out of limit, rotten egg smell from exhaust & reduced speed
Possible solutions
- Replace the catalytic converter
- Replace any faulty oxygen sensors
- Repair any exhaust leaks
- Check and repair any fuel system problems
- Check and repair any ignition system problems
- Check for any engine mechanical problems
Free on OBD DashX
P0420 on OBD DashX
Real-world causes, how often this code shows up, and the fix — step by step.
Open P0420 No sign-up needed · available in 10 languagesScan your own car
Read and clear fault codes, live data and service resets with the CaRPM app.