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#1 Old Jun 27th, 2003, 07:19 AM
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CEL: code P0400 (EGR Flow Malfunction)

My check engine light went on yesterday, so I took my car to Autozone and used their OBDII sensor to scan the code for free. The code was P0400 EGR Flow Malfunction. I called a mechanic, and he said it's probably a problem of dirty tubes, but he couldn't get me in until next week.

My question is this: is it plausible for me to just buy a Haynes manual and clean out the EGR tubes myself? I'm not too experienced in working on my vehicle, but I'd rather not pay $200 for someone else to do it when I can do it myself in my driveway with my car on ramps.

Suggestions?
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#2 Old Jun 27th, 2003, 11:36 AM
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Ah, the Engine Gas Recirculation System
I am looking at my haynes manual right now, and it's looks like a royal pain in the ass. let me write some of this in for you, to give you an idea of the different possibilities of your problem

"The EGR system is used to lower NOx (oxides of nitrogen) emission levels caused by high combustion temperatures. The EGR recirculates a small amount of exhaust gases into the intake manifold. The additional mixture lowers the temperature of combustion thereby reducing the formation of NOx compounds."

-EGR recirculates exhaust gasses to the intake.-

"The EGR systems are equipped with an EGR valve and also an "EGR and canister control solenoid valve" which recieves ported and manifold vacuum. The operation of the system is controlled by the ECM which operates the control solenoid valve. The manifold vacuun system utilizes a vacuum tap in the air intake system positioned after the throttle valve. The ported vacuum control system uses a vacuum tap in the throttle body which is exposed to an increasing percentage of manifold vacuum as the throttle valve is opened during acceleration."

-The EGR valve + Canister Control Solenoid valve work together to controll the flow of the exhaust gas into the intake. When the control solenoid valve is instructed to open by the ECM, this in turn opens the EGR, which then using vacumm, starts the system from the Canister to the intake. The more air that is sucked through the throttle body, the more exhaust gas is pulled from the system by vacuum.-

"A backpressure transducer (EGRC-BPT) valve monitors the exhaust backpressure as the engine RPM increases or decreses to aid in controlling the EGR vacuum signal. An EGR temperature sensor is also used to inform the ECM of the heat in the exhaust gas which is being supplied to the engine."

The EGRC-BPT simply makes sure that the exhaust backpressure doesn't overpower the intake vacuum. The temp sensor aids in the ECM's tuning of this function.-


If something in your system is clogged, it may be a vacuum line (which can be checked), or the actual exhaust return pipe (doubt that can be clogged).
Addition malfunctions can be attributed to the EGR valve + Canister Control Solenoid valve. If one of these solenoids were to fail, the system may either be stuck open, or stuck closed.


The haynes manual does give the instructions for how to
Replace the EGR valve unit.
Replace the EGR + canister control solenoid valve
Replace the EGR temperate sensor.

If you would like more info on any of these repairs, I can post it for you, but take a look around, try and diagnose the problem, my fingers are too tired to type the next page ..... for now.

Hope that helps you out.
#3 Old Jun 27th, 2003, 11:59 AM
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Wow, that was an AMAZING post! Thanks for all the information! Do the instructions for replacing the EGR Valve (which, I'm assuming is near the hoses I need to clean) look like it's in a tight or difficult space? I'm trying to figure out how much time/energy I'll need to clean them out.

Thanks!!
#4 Old Jun 27th, 2003, 12:36 PM
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I took a look under the hood of my car, and it is a tight fit. Your best bet if you are going to clean all the hoses out, is to remove the Air Intake + filter box. This should only take 15min, or so. If your car gets rust, don't detatch the air-box from the engine bay, the bolt's may snap off when you try and unscrew them.
Make sure that you label the hoses before removing them, it's a slightly tricky configuration of 2 ro 3 hoses. There should be 2 hoses that run to the intake manifold, 1 at the throttle body, 1 after the TB, then a hose going to the EGR valve, and a hose going to the EGRC-BPT valve. Any cleaner that is safe for rubber will work (brake cleen might, read the bottle for warning, or ask an autozone guy what to clean the hose with). After you reassemble, the hoses + air intake, go to autozone, have them clear the error code out of the memory, and drive. If the light pop's up again, you most likely have a busted solenoid.

The haynes manual doesn't have any instructions for hose removal or cleaning, so I would ask a nissan mechanic for any specific questions you have.

I was also thinking, having your EGR system not working may be bad for the environment, but I bet you get an extra .25 horse power. Hell, I'd kill a baby seal for that?!?!

Good luck
#5 Old Mar 26th, 2004, 03:11 AM
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Unhappy EGR 97 200sx GA16DE code 0302 egr function.

My baby is throwing an egr code too. Thought it was an o2 sensor becuase the readiness would not reset on my obdII meter.
Found out by doing the ECU screw thing it is code 0302 for the EGR and my o2 finally reset (went and bought 2 new sensors anyway before I knew)
The EGR cleaning could be done with TB cleaner? Probabally the valves are dirty (all or 1 or just a clogged tube) I tried getting to the valves but in my opinion it's worth it to just pay a poor grease monkey (not me) to break his/her (PC) knuckles and put a hunch in their back for a lousy $200.00!
This crap is just too hard to get to or get out or figure out so there.
Why would this be clogged or the valve shot at 75K miles anyway?
I thought this engine was good for 250,000 mi if not more?
Anyway, I'm enjoying the extra HP and can clear the code for emissions so maybe I'll just emit NOX and go fast hah!
I am so glad I will be buying classics from now on and not modern computer controlled (more like impaired) engines.

Last edited by DanTheMan; Mar 26th, 2004 at 03:17 AM.
#6 Old Mar 26th, 2004, 08:53 AM
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My car threw that code a while back. Turned out to be a busted vacuum line, easy fix.

Sentra & F4
#7 Old Mar 26th, 2004, 10:09 PM
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i hate that code totally irritating EGR code.

mine been on forever.

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95 200Sx SE-R - work in progress

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#8 Old Mar 27th, 2004, 03:38 PM
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Are the vaccuum lines the same that are used for the windshild washers? Or are they different.
#9 Old Mar 28th, 2004, 10:36 PM
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another test is to actually push the EGR valve from undernieth... you can fit your finger undernieth the saucer while the car is running.

if you push it up and the car stalls and or dies... the egr valve works. Then clean the lines with super solvent and go on your way . you might have to just take off the EGR valve and lines anyway to look into the manifold to see if there is blockage (KA powered trucks are notorious for this, the design of the intake makes the EGR ports get caked in soot, its normally rock hard and takes some time to clean properly)

-Corey
#10 Old Mar 29th, 2004, 02:21 AM
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Smile EGR Hotshot Tri-Y Ga16de 1997' OBDII

Quote:
Originally Posted by lawabidn
another test is to actually push the EGR valve from undernieth... you can fit your finger undernieth the saucer while the car is running.

if you push it up and the car stalls and or dies... the egr valve works. Then clean the lines with super solvent and go on your way . you might have to just take off the EGR valve and lines anyway to look into the manifold to see if there is blockage (KA powered trucks are notorious for this, the design of the intake makes the EGR ports get caked in soot, its normally rock hard and takes some time to clean properly)

-Corey
Yeah man, Looks like the tubing was bad/clogged? Was able to check the tubes, spray cleaner in there and when I pulled on one between the valves it just disintigrated in my hand, at least the end did, and in the middle was this lump, really hard, and I'm like is this a chunk of soot or what?
NO! It was a little metal (brass?) piece that is round around the diameter and about as wide as the tube with this pinhole (yeah a pinhole in the middle)
Now is this a dislodged valve part (EGR valve broken?) or is it supposed to be in the tube obstructing the flow? Great design!!! This pinhole won't flow nothin so I chucked it. If it works great, if not it's valve time, I think my new silicone hose and the lack of the little metal pinhole cork device may make a slight improvement in the EGR flow.
I will check to see if it's functioning with the push the valve test tomorrow.
I've only driven once since so I'll give the ECU time to see multiple trips before I can say "fixed".
I would sure love to pass emissions and this is a BS code anyway.
TO pass emisions I can also just clear codes and reset all sensors but one or two of the "emissions readiness monitors" and they have to pass it because the light "works" and the CEL is "off" and a 96-98 can have up to two monitors not ready. This goes for 02 cat egr etc... but only two.
You will wanna check the monitors prior to pulling in to assure only 1 or 2 are not set more than two =fail. In this way you can pass "between codes" or before the ECU triggers the code but has set most monitors. HEHEHEEHEHE.
#11 Old Mar 30th, 2004, 09:40 PM
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Cool update

I tried the "push the valve" test and the engine dyied like it's supposed to,
so far so good no code yet but I know the o2 sensor readiness is still not
set so I'm keepin' my finger crossed. All the other emissions monitors are
"ready" so they have reset. I think without that metal piece stuck in the tube It should be fine now.
Still don't know where that came from/ what the hell it was.
Any Ideas? shapped like this... o whith a pinhole in the middle, just a circular piece of brass. It was in a vaccuum line between the egr valve and some other valve. ???
All I know is no codes means OK and my AutometerOBDII thingy will tell me if it's ready for emissions when all the sensors reset.

He who claims he knows all is ignorant,
He who claims ignorance is on the path to enlightenment. Lao Tsu
#12 Old Mar 30th, 2004, 11:39 PM
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Im not familiar with that Imparticular peice, but I know for a fact Nissan does put peices like that in particular hoses for flow management.

SOunds like a factory piece, but if it fixes it... so be it!

-Corey
#13 Old Mar 31st, 2004, 10:29 AM
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Brass fitting

There is a brass fitting leading from the EGR & canister solinoid and the resonator. You might want to check to see if theres anything connected to the resonator. The brass piece is an adapter of sorts to connect a larger piece of tubing so you can connect the resonator. It is possible that you pulled the brass piece off the larger one. I just replaced all my hoses, and this brass fitting.
#14 Old Apr 1st, 2004, 12:56 AM
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Talking Brass "fitting"

Yeah, thats prob. what it is/was hahahehe. No more codes and all my emissions readiness monitors are reset (god I hate this 97 ECU with OBDII, JWT won't touch it either). This means the repair is "confirmed". It was the brass thing stuck in a vacc line and that particular line dry-rotted out way early for some reason. No matter , a nice piece of left-over silicone hose from my HS intake took care of that and the lack of obstruction and/or vacc leakage has repaired the egr flow/function.
Joy!
This code is so irritating!
Thanks for the input guys

He who claims he knows all is ignorant,
He who claims ignorance is on the path to enlightenment. Lao Tsu
#15 Old Jun 26th, 2008, 10:18 PM
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I just replaced my blown head gasket and the cyl head on my 96 Sentra. Before I did it, I was getting water/oil mixed which clogged my MAF sensor. Everything is all replaced and the car runs great now, but I'm getting a P0400 fc. Is it possible that some of this water/oil froth gummed up my EGR?

Dean
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