Hi! So I have a v6 3 liter 2000 Honda accord. The check engine light has been on for about 4 years straight with the P0401 code. I have replaced the egr valve four times and had the manifold cleaned out extensively by different shops and the shop that I now work at. My coworkers did a major deep cleaning for free for me but the light stayed on! Usually I’ve managed to clear it for at least a few weeks to get it skogged when I get a new egr valve, but this year it will not clear no matter what we do. Brand new egr valve, spotless manifold, new MAP sensor…does anyone have any suggestions for what I could possibly try next?? My registration was due 2 months ago, it’s paid but I can’t get my tags until I get a smog!

 

I don't have answer but I do see vacuum line leaks can be an issue. And there seems to be a service bulletin.
https://www.google.com/search?q=P040...obile&ie=UTF-8
https://www.justanswer.com/honda/ac0...1-cleaned.html