P0423: Heated Catalyst Efficiency Below Threshold (Bank 1)
HighPowertrainCatalytic Converter
What does P0423 mean?
P0423 is a diagnostic trouble code indicating "Heated Catalyst Efficiency Below Threshold (Bank 1)". The catalytic converter in your exhaust system is not converting harmful gases as efficiently as required. This affects emissions and may indicate the converter is failing or there is an upstream issue.
Common causes
- Aging catalytic converter
- Engine misfire damaging the converter
- Oil or coolant entering the exhaust
- Faulty downstream O2 sensor giving false reading
What should you do?
This is a significant issue that should be diagnosed and repaired soon. Avoid long trips or heavy driving until the problem is resolved. Continued driving may cause additional damage.
Get a diagnosis for YOUR car
Code P0423 can mean different things depending on your vehicle. TorqueBot gives you a diagnosis specific to your make, model, and year.