I have a '01 Accord 6 cylinder. In April 2017 it failed the smog test for multiple codes. p0401,0705,0706,p1491,p0302,03030304,0305 and p1399. I replaced the EGR valve, IAC, and MAP sensors. I removed upper intake and cleaned the port discovering I didn't need to replace the "pipe". still pulled P0401 and misfire codes. Sat for a year, then last month replaced all six coils. Runs great but still pulled P0401 code. Tested EGR and found no continuity. Replaced EGR again, and still pulls P0401 code but otherwise runs great. Today I pulled intake again and cleaned small "side "passages yet still pulls P0401. Just for the heck of it I tested EGR again for continuity and it has none. What is going on? Where do I go from here.

Should I pull the lower intake and "Hot Tank" it or can I clean it myself with carb cleaner or such?
Is there something else I should be looking at?

I'm getting really tired of this code.

 

I am having the same issue now. What fixed it?