Code P0401?

IFYUSER

MEMBER
2002 HONDA CIVIC
1.7L
4 CYL
2WD
AUTOMATIC
190,000 MILES

I have a p0401. I already changed the EGR valve and tried to clean the EGR passages soaking them with seafoam and still get p0401. What's weird is the port that expels exhaust when I leave the EGR removed and the car running gives exhaust I can feel it with my finger. What could be the problem? I also sprayed throttle body cleaner in the intake port in the EGR port while running.

5 Replies

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

Do you feel exhaust from the EGR side or the engine side? The EGR recirculates exhaust gas through the intake manifold and into the combustion chambers. If you remove the EGR with the engine running, it should cause an adverse condition as far as how the engine runs.

If you have a new EGR and everything is clean, it could be an electrical issue. If you look below, I attached the diagnostics for the code you have. Take a look through them and let me know if you are comfortable performing them.

Take care and let me know what you find.

Joe

See pics below.

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Thursday, January 26th, 2023 AT 4:03 PM

IFYUSER

MEMBER
54 POSTS

I checked it again and I think the EGR passages are clogged when I put current it clicks, and the car won't stall. Also, it won't stall with the EGR removed. I poured seafoam on the exhaust side, and it doesn't drain down, but it does drain down when I pour it in the intake side. Do you have instructions to remove the intake manifold?

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Friday, January 27th, 2023 AT 7:10 PM

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

I would be happy to provide the directions, but I just went through two manuals and found the exact same thing for removal and replacement, an exploded view.

Take a look at it and see if it helps. I'll be here if you have questions.

Take care,

Joe

See pic below.

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Saturday, January 28th, 2023 AT 8:16 PM

IFYUSER

MEMBER
54 POSTS

I was looking at the picture would a intake manifold gasket leak on this car because the p0401 despite that the car doesn't stumble when the EGR valve is off the car and running at idle.

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Saturday, January 28th, 2023 AT 9:24 PM

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

That is a good question. However, I don't feel it would set the code you have. Something is restricting EGR flow. If the intake gasket was leaking, I would suspect to find a lean fuel mixture code, a random misfire, or the vehicle would have a high or rough idle.

Let me know what I can do to help.

Take care,

joe