So, I have had my check engine light on for a couple months now and decided to start trying to take care of it and get it fixed recently.

The code I am pulling is the P0401 for insufficient EGR flow.

I have already replaced the valve itself and ontop of that I just had the intake manifold completely cleaned out. I also had the injectors and fuel system cleaned while i was at it.

So, my question is, if anyone has ran into this problem or knows what it could be. I dont even know where to go from here and am wondering if I should just begin to look for a new car because of the miles.

Oh, the car itself, it is a 2001 Honda Accord, 2.3L 4cyl with 239,000 miles.

If anyone has any insight into this problem or a way to fix it it would be very greatly appreciated.

Thank you in advance.

 

Have you cleared the P0401 code from your car's computer since making the repairs? If not, clear it, and then take a drive long enough for the EGR to open like it's supposed to and see if the code comes back. If it doesn't and your car is running okay, you're good to go. If it does come back (or if you've already tried this) then you'll have to look at the EGR system again. The code comes from the valve so that should be your target. You can use a vacuum pump to operate the valve manually a few times and make sure its mechanically sound. If you still have it, you could also try cleaning it up and putting your old EGR valve back in. While those old parts don't last forever, they were built to last a very long time.

 

Thanks for the ideas! I have cleared the code and ran it for a long drive and it came back on. I just reset the code again an am going to see if it comes back on, hopefully no because if it does that is where i am stuck. Could it possibly be the relat to the egr valve itself that would make it trigger the code?

 

Fairly exhausted right now, but as I recall the EGR system also has a lift sensor and, or control solenoid. If you're handy with tools, you could get a Haynes Manual and it will tell you what to look at and multimeter test/ check inside the vacuum box, which is the thing if you trace the EGR hoses, leads to that box.

If you still have your old EGR valve, I would seriously consider putting it back into service. Keep in mind also that a lot of so-called upper engine, intake manifold cleanouts are not what they are cracked up to be. Especially not on EGR designs like Hondas. If I were you I would get under the hood and have a look at those EGR passages myself. You have the fairly easy kind to inspect. On the older Accords (like mine), the job was like doing surgery on the car. Referring back to the EGR Solenoid inside the black box. Checking it would be wise if all else fails. I'm pretty sure I was wrong, and that is the thing that put the code in the computer. Srry I can't try to help more right now.

 

Well thank you ver much! If it comes back on again i am gonna have to check into those and i will look into putting the old egr valve back on this weekend as well! I will check on the egr passage as well myself to make sure they cleaned that all out! Again thank you for your help, much appreciated.

 

The passage in the corner of the upper intake cap is likely plugged.

 

You have to take it apart and get in there clean the passages, with throttle cleaner carb cleaner etc.

 

I have already taken the throttle body apart and cleaned it out.... Thats why im stuck. I cleaned it out this weekend and it is still pullin the code...

 

Open the EGR valve at idle. The car should die. If it does, the passages are open, obviously. If the car does not die the passages are plugged.

Remove the EGR valve and start the car, the intake port should suck and the exhaust port should blow. This is one way to tell which side of the passage is plugged, the intake or the exhaust.

While I suppose it's possible, I have never had a faulty EGR valve cause a P0401 without also having a P1491 ( insufficient lift ) or other lift position related DTC.

The most common location for a blockage in an EGR passage is near the intake manifold due to the fact that the exhaust gases have cooled down due to the colder temperature of the passage as the passage nears the intake area.

I have repaired many P0401 DTC's on your year/engine by cleaning the carbon blockage right where the EGR passage enters the upper portion of the intake right behind the throttle body. This is only accessable by removing the upper cap on the intake and scraping the chunk out of the cavity.

If you've cleaned this, cool. Perform the checks I mentioned to confirm and find the blockage.

 

Hi Oldmangold,
I have a 99 EX 4 cyl and just did the throttle body and egr cleaning this weekend and I am still getting the cel coming on even after resetting the cpu by pulling the 13th fuse on the passenger side. The Haynes manual says there is a way of testing the actual EGR and that is by turning the car on and letting it run long enough for the cooling fan to come on. Then shut car off and disconnect the EGR valve electricalcal connector. Install a fused jumper wire from the battery positive terminal to terminal #4 on the EGR valve then start car and connect a jumper lead from the battery negative to terminal# 6 on the EGR valve. The engine should run rough and or stall. If it does not then replace the EGR....make sure not to apply the battery voltage to the harness as this may fry your PCM.

 

if all else failes, try opening your ecu box and looking for burnt electrodes.. just had this happen with my civic throwing different codes. spent over 200 dollers on sensors, and it turned out to be my ecu. worth a try..

 

I have found a ton of information on cleaning the EGR Valve and Passages on similar Hondas, however my 2001 Accord 4-cylinder 2.3L Engine has different EGR passages than what I've found online.

I have taken off the valve and cleaned it, and cleaned the ports that connect to the valve. My "check engine" light now takes longer to come on, but is still coming on (diagnostics and emissions have linked this to EGR flow insufficiency). I think my next step is to clean the passages.

Does anyone have any information on how to do this? I have the tools, and am pretty certain on I can do it, I just need some guidence. It's either that or my mechanic quoted me at $350.

 

Hi Katez,
I know how to do it and can give you the info on how to do it.
I can get back to you tomorrow with more info.
In the meantime I would suggest that you get some things to have before you attempt the job.
I would have on hand at least a foot or two of the following size hoses.
3/16,1/4 and 5/16. Also buy the upper plenum gasket ( they cost about 5 bucks at autozone ) also buy the IAC valve gasket ( dealer part) since you will have to remove it to get the throttle plenum off. Also there is a gasket where te throttle body meets the plenum ( you may or may not want to change this too, I did )

Tomorrow I will get into the process I just wanted to answer the thread.

 

Hi Katez,
Unfortunately I cant post pics due to my account but I will try to be as detailed as I can. If you need any help just let me know.

Disconnect the negative terminal off the battery just for safety reasons. Drain the coolant so that later on you won’t have a coolant mess when you remove some coolant hoses. Disconnect the air tube, map sensor connector and vacuum hoses (label them as to where each goes )( If they are difficult to get off or look suspect this would be a good time to replace them with the spare hoses you should have on hand when reassembling. Now you will have access to the 2 bolts and 2 nuts which are on the throttle body. I believe they are 10mm bolts. There are 2 bolts in a diagonal pattern which you will just have to feel out that have to come off which are on the right side ( passenger side ) that hold the air control valve onto the IM. There is a filter and 2 hoses attached to this air control valve that I would replace since a leak can develop here later on. You will also have to disconnect the PCV valve which just pulls off. Take off a couple bolts that hold the throttle and cruise control cable onto the body of the IM (intake manifold) (try to be careful with this as you want to avoid the cables from coming off) There is an electrical connector coming off the fuel rail that you will have to disconnect as well it is being held by a couple bolts onto the body of the IM. Next remove the air temperature sensor assembly on the left side ( drivers side of the IM) There are (2) bolts under the sensor assembly that also have to come off. One is holding a bracket and the other is extremely important as it is the main ground for the ECM. I think that at this point all the attachments are off. All you have to do is remove the 5 bolts ( 2 in the front and 3 in the back of the IM) and it should come off. Have on hand at least 2 bottles of carb cleaner and hit the passages of the IM once you have it out. You will see a chunk of carb build up on one corner. It might be a good idea to have a small wire brush as well. You can spray some of the carb cleaner into the throttle but don't over do it. Now let everything air dry a bit and reassemble. You should definitely feel a little bit better zoom and gas mileage should improve slightly but best of all the annoying CEL will be off!. Good luck and give yourself 4-5 hours to do this. Laterz.