OBD2 CodesApr 13, 20268 min read
P0420 Code: What It Means & How to Fix It
The P0420 code means your catalytic converter efficiency is below threshold. Learn the causes, symptoms, and step-by-step fix.
What is the P0420 Code?
The P0420 diagnostic trouble code (DTC) indicates that your vehicle's catalytic converter is operating below its efficiency threshold.
Common Causes
- Failing Catalytic Converter - Converters wear out over time, typically lasting 100,000-150,000 miles.
- Faulty Oxygen Sensors - A bad O2 sensor can trigger false P0420 codes.
- Exhaust Leaks - Leaks before the catalytic converter can cause incorrect readings.
- Engine Misfires - Unburned fuel entering the converter can damage it.
Symptoms
- Check Engine Light illuminated
- Decreased fuel economy
- Failed emissions test
- Reduced engine performance
How to Fix
- Replace Oxygen Sensors ($50-150 each) - If sensors are faulty
- Repair Exhaust Leaks ($100-300) - Patch or replace leaking components
- Replace Catalytic Converter ($500-2,500) - If the converter is confirmed bad