← Back to list

2000 Honda Accord V6 OBD Codes P0420 and P1399: Cat Failure or Misfire? Diagnosis & Solutions

Model: 2000 Honda Accord v-6 Fault Code: P0420 Posted: 2008-04-08 13:57

I own a 2000 Honda Accord V6 with only 68,000 miles on the odometer. Recently, I've been receiving two OBD-II diagnostic codes: P0420 and P13909. Initially, the vehicle showed an EGR valve issue. I removed and cleaned the EGR valve, and also had carbon buildup cleared from the EGR housing. A fuel induction service was performed to remove any remaining deposits. Since then, the EGR-related code has not returned. The current codes are P0420 (Catalyst System Efficiency Below Threshold) and P1399 (Random/Multiple Cylinder Misfire Detected). I'm wondering if it's possible that the catalytic converter is actually failing. Given that the car is 8 years old, the catalytic converter has reached its federal emission lifespan of approximately 80,000 miles. What should I do next? Should I have the catalytic converter inspected or replaced? Are there any specific diagnostic steps to confirm whether the issue lies with the cat or a misfire? Any advice on how to interpret these codes in this model would be greatly appreciated.

Related fault codes
P0420P1399
Comments (3)
Anonymous 2008-04-08 14:05

Have you searched online or in the Honda Accord service manual for specific meanings of P0420 and P1399? Understanding what each code indicates is crucial before taking further action.

Anonymous 2008-04-08 15:13

The catalytic converter on a 2000 Honda Accord is a federal emission component with an expected lifespan of around 8 years or 80,000 miles. Check if your vehicle is covered under warranty or recall by contacting the dealership. Note that P1399 indicates a random/multiple cylinder misfire—this should be addressed before discussing catalytic converter replacement. Clearing this code may help determine whether it's truly related to engine performance.

Anonymous 2008-09-27 07:59

Did you verify if your vehicle received the service recall for EGR port redrilling? For all 2000 Honda Accord V6 models, the EGR port needs to be re-drilled to ensure proper airflow and prevent sticking. This is a known issue that can trigger P0420 codes. To confirm catalytic converter failure, monitor the O2 sensor readings before and after the catalytic converter—any significant drop in efficiency indicates a failing cat.