GMC Error Code P0420: How to Fix It

Q: Can I drive my GMC with P0420 code?

Yes, you can drive short distances, but the vehicle will fail emissions testing and fuel economy may decrease. Address the issue promptly to avoid potential engine damage and ensure compliance with emissions regulations.

Q: How much does it cost to fix P0420 on a GMC?

Costs vary widely depending on the cause. Oxygen sensor replacement costs $150-300, while catalytic converter replacement can range from $500-2000 depending on your specific GMC model and converter type.

Q: Will P0420 clear itself on my GMC?

No, P0420 will not clear itself. The underlying issue must be repaired, and then the code needs to be cleared with an OBD2 scanner. The system will need to complete several drive cycles to verify the repair.

Q: What causes P0420 in GMC Sierra and Yukon?

Common causes include failed catalytic converter, faulty downstream oxygen sensor, exhaust leaks, engine misfires, contaminated fuel, or oil consumption issues. Higher mileage vehicles are more susceptible to converter failure.

Abstract

GMC error code P0420 indicates that your catalytic converter isn't working efficiently on Bank 1 of your engine. This common issue in Sierra and Yukon models means the converter isn't properly reducing harmful emissions. While not immediately dangerous to drive, this code will cause your check engine light to stay on and your vehicle to fail emissions testing.