OBD-II Generic Error Code P0420: How to Fix It

Q: Can I drive with P0420 code?

Yes, you can drive with P0420 but it should be addressed soon. While not immediately dangerous, it indicates your vehicle is producing higher emissions and may fail an emissions test. Prolonged driving could worsen the problem and lead to more expensive repairs.

Q: Will a bad oxygen sensor cause P0420?

Yes, faulty oxygen sensors are a common cause of P0420. Bad sensors can provide incorrect readings to the ECU, making it think the catalytic converter is failing when it's actually working properly. Always test oxygen sensors before replacing the catalytic converter.

Q: How much does it cost to fix P0420?

Repair costs vary widely. Oxygen sensor replacement typically costs $150-400. If the catalytic converter needs replacement, expect $800-2500 depending on your vehicle. Always diagnose the root cause first to avoid unnecessary catalytic converter replacement.

Q: Can I use catalytic converter cleaner for P0420?

Catalytic converter cleaners may help with minor efficiency issues but won't fix a truly failed converter. They work best as preventive maintenance or for very mild contamination. If P0420 persists after using cleaner and addressing other issues, converter replacement is likely needed.

Q: Why does P0420 keep coming back after repair?

Recurring P0420 often indicates the root cause wasn't addressed. Common reasons include: using cheap aftermarket parts, not replacing oxygen sensors with the catalytic converter, unresolved air-fuel mixture problems, or exhaust leaks that weren't found during initial diagnosis.

Abstract

Error code P0420 indicates your vehicle's catalytic converter system efficiency has dropped below the acceptable threshold. This means the catalytic converter isn't cleaning exhaust gases as effectively as it should, which can affect emissions and fuel economy.