I'm getting a code of P 0401 on my '99 5.4
F-250. This code is "exhaust gas recirculation flow - insufficient". Anyone have any experience with this before I start trying to diagnose. Looks like it should be confined to the EVR, EGR valve or DPFE sensor. Appreciate any information anyone has. Thanks

 

How do you "read the code"?



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TexasDude * * * *
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'99 F-150 XLT S/C, Flareside, 4.6 V8, Auto, 3.55 LS Axle, Tow/HD Suspension Package.

2001 Expedition XLT. 5.4 V8, Leather, 6CD, Running Boards, 3.55 LS Axle. My wife loves it (and I rarely get to drive it ).

The only things modified are my attitude and bank account!

 

Rustty,
I have gotten the same code on my 95 Crown Victoria. I took it to a Ford mechanic and he checked it out for me. Here is the story. The EGR system on the 4.6 is very sensitive and the slightest blockage of any type in the EGR system will set the 401 code. Yet the vehicle will continue to run like a swiss watch. The most common cause is carbon buildup at the base of the plenum and in the metering tube between the EGR Valve and the manifold. There is a Ford bullitin that talks at length about this problem and how to fix it. Basically you have to clean out all of the EGR passages of carbon buildup. To have a mechanic that knows what he is doing fix it for you will run around $350 to $450. If you know what you are doing and you have a copy of the bullitin you can do it yourself for the cost of the gaskets. Remember that direct fuel injection systems are dry top systems. Meaning that no fuel flows through the areas between the throttle body and the manifold. So over the long term, say around a 100,000 miles carbon will build up to sufficant levels to start blocking vital passages and thus will cause the ODBC system to start throwing fault codes.
TDC

 

To Texas Dude: I was showing a "check engine soon" light on my dash, however, the truck was running fine. I called a few mid to small size shops around here and they all wanted $60 to $70 to read the codes. And of coarse, you have to leave the vehicle for the day. I decided to go to Autozone where I bought the Actron OBD II diagnostic tester for $150 - about what it would cost for 2 scans. The scanner connected easily on the connector under my dash and I got my readout. The whole process took about 1 minute.

TDC: Thanks for the information. I've heard about this problem on 4.6's and it probably applies to the 5.4. Let me know where I can find the memo from Ford if you know, otherwise I'll do some more checking around. Sounds like all 3 components could check out okay, and you still have the problem.

 

Rusty,
The Special Services Bullitins are listed in the Popular Mechanics Automotive Repair Software from Alldata. You can buy it at Autozone where you bought your scanner. I highly recommend it. The software in conjunction with your scanner will help you alot. These particular software packs are very thorough and detailed. I think you will be pleased when you test fly it the first time. They take a little time to figure out how to navigate but once you got it down they are easy to use. And yes you are correct. You can replace all the EGR components and still get the 401 code. The carbon buildup has to be manually removed. I am an old time motorhead and I long for the good old days of points and Big giant carbs. But they are gone so we have to use the correct tools on our vehicles and unfortunately that means software and electronic gadgets. Good luck pal. If there is anything I can do assist just give me a yell across the net.

Regards
TDC

 

Sounds like the valve to me being clogged to. Give it a few taps if you don't want to remove it a clean it. Did this to a buddies of mine who has a 94 T-bird with a 4.6L. Works good now.

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1998 Ford F150 4.2L V6
American Racing Rims
Brush Gaurd
Tinted Windows
Saving for lift and SuperChip
3.55 Rear
5 Spd.

 

Just found this and I am having the same problem. It first started out as I was getting a code 402 which is EGR flow excessive, after getting that code about 6 times in a 2 day period I started getting code 401. I checked all the connections ( no actual testing done yet) and tapped on the EGR with a screwdriver. The tapping solved it for about 2-3 days but now it's back.
I am going to use my new DMM to test the DPFE and EVR TO test the EGR I need a vacuum guage. I figured if it's not the EVR or DPFE I think I have found an new EGR valve for $33 which is cheaper than a vauum guage. I know just changing it might not solve the problem but I can change it and clean it to be sure I have the problem.
Would most agree that this is the best corse of action or should I do something else? Can anyone explain why I got code 402 and then a code 401?

 

po402 is getting flow at idle. and po401 is not enough flow. with both codes its like yours is sticking open then closed. for a 401. if you apply vac to egr and engine stumbles. the passages are ok. if you can monitor pids. or voltage of dpfe. key on engine off volt should be around one volt. like .97volt around there. if it read's .14volt or .49volt. you need a new dpfe.if you can mointor that voltage. apply vac to egr with engine running and see if it goes up. from 1volt to about 5volts. good luck.

 

Unfortunately I can not monitor the PIDS with the Actron OBD II scanner.Wish I could, that would be the easy way to test them. I can and plan to use my digital multimeter to test them. After this is fixed I'm going to try and sell the code scanner and multimeter (both pratically brand new) and get a better tester ( Auto x-ray, etc).

I thought it was weird the first 6-8 times the MIL came on it was code 402. After I tapped on the EGR and DPFE all I get now is code 401. My logic (without testing) is that the EGR is carboned and sticking open or closed. I can usually pretty much predict when the MIL will come on now after the code has been erased. It pretty much seems to happen right after I have driven 11 miles on the interstate at about 2000 RPM's (75 mph). I can drive a very short distance (interstate or non-interstate) and get the pending code 401 and not too much later the MIL will come on.

I have found a parts place around here that sells a Motorcraft EGR for $33. I found this to be a great deal (hoping is not a reman) considering I work at another parts place and ours is almost double that and we are out of stock. The cost of a new EGR is less than the cost of a vacuum guage that I would need to test the old one with. So I'm hoping I can test the DPFE ($75 part)and maybe the EVR and then use the new EGR if I have too. If this doesn't work I might as well give up and take it to someone before I buy all these unneeded parts and $300 worth of test equipment.
Thanks for your help.

 

Here's the rundown.
The EGR valve I had ordered was totally wrong even though I gave the idiot the OE part# it still seemed to f@#K it up. They are supposed to be ordering another EGR. Their computer's # for the EGR didn't match mine but he called local Ford dealer and said mine was discontinued and replaced by this one. I will try and call to verify this before I put it on if it's needed.
I did go ahead and check the EVR and the DPFE but like Russty am a little puzzled by results.

EVR
KOEO- should be battery voltage- I got 12.25
Ohms reding of sensor should be 30 -70- I got 33.20
So the EVR seems to be fine

DPFE
Connector unplugged and testing harness side
KOEO- reference voltage 5.02
KOEO-signal voltage 5.02

Harness connected to DPFE and backprobed, book didn't say to do this but I wanted to try it anyways.
KOEO reference voltage was 2.84

Harness connected and backprobed engine was not completly cold like it would be sitting over night.
KOER reference voltage was 5.02
KOER signal voltage was 2.84, this is all I could get (should be .20-.70 cold and 4 - 6 volts at operating temp) I think this is how Haynes says to test it I am not for sure with thier wording.

Note: I was unable to get much if any reading when I was trying to use the multimeter's test leads. So I used a straight pin (like you find in a new folded shirt) as probes and then tested against them. I pushed them as far as possible into the back of the connector without puncturing the wire. Do not know if this is the correct way or not

 

wino hit it right on the head....if you have a P0401, start the vehicle, let it idle. Find a length of vacuum hose that fits over the nipple on the valve, and is about 2' long. disconnect the factory (red) vacuum line from the valve. While it's still idling, start to suck on the hose-it doesnt take much to get flow. 2 things will happen-the idle quality will get poor, and the egr tube from LH manifold to egr valve will get hot as exhaust flow comes thru it. If these two things happen, the valve is functional. Next, perform a KOER test-if a P1408 is set during the test (disregard P1127) it's almost a gimme that the DPFE is faulty.
P0402's are commonly associated with rough idles because the code is for uncommanded flow. If the idle is ok, it's usually the DPFE as well. It it has a horrid idle, you probably have a valve that's stuck partially open. Tapping it will fix it for a day or two, but in my experience, if it did it once it'll do it again.
Note-on late '01 and all '02's, with the DPFE that doesn't attach to the intake manifold, and is a small black sensor that sits on the sensing hoses with a rectangular plug in, these are absolute GARBAGE and are failing left right and centre. it's happening on all ford vehicle lines....it's the most common emissions failure lately. Backordered from here to eternity, which is a good sign that something will be done soon. heads up, kids

 

Sorry to be a nudge here but are we missing the point? (With the exception of the newer DPFE) In my many years of experience the EGR valve almost never goes bad (I said almost never) In 9 out of 10 cases it is just carbon build up in the "System" the whole "System" not just the valve. The build up occurs faster if you use the wrong octane gas.

But all I read in here is the testing of the sensors! If the EGR "System is clogged the sensors will fail, you can replace them and they will work great until they glog again. And do not "Tap" your EGR valve! All you are doing is knocking bits of carbon into the system which will just lodge themselves into somewhere they shouldn't be.

In a nut shell just clean the system first THEN check the sensors!

just my .02

good luck-

 

I would be more than happy to clean the entire system if I only knew exactly what to use. On everything I have read it says not to use any kind of solvents on the EGR or any of the sensors.
What gets me is these things are made to live in the rough environment of truck conditions and are suppsoe to handle exhaust gas all day but you can't even use a simple cleaner on them.
I am going out right now to pull the EGR valve off and clean it by hand after I retest the DPFE. If it looks very bad I have a new one standng by to put on. I don't think it is going to solve my problem but it seems like no one can answer what I need to know. I now know how to test the EGR valve but, I need a vacuum guage which i don't have but, I might be able to pull a vacuum from something else.
What I really really want/need to know is if or how I screwed up the testing on the DPFE. Like I said I had to use stragiht pins to backprobe the sensor and even with the engine warm I only got 2.84V when I used the signal side of the connector (top) as my hot and the middle connector as my ground.

 

Ahhh, this friggin thing is driving me nuts. Now I do not even know if I am testing the right spots on the connector. Bear with me this may be long and it may be to confusing to even explain correctly.
On my connector there is three wires, top wire is a brn/lt green, middle is gray/red, and bottom is brn/white. I know the middle is the ground or I think some call it the signal return. Now here's the problem. On that connector is a notch on the front side BOTTOM that must lign up with a lip on the sensor. They even show it that way in the Haynes manual picture but their diagram for the wire locations is flip-floped. They have the notch of the connector on the front TOP. Their words, picture, and diagram just don't match. So basically I just need to know what the top wire and what the bottom wires is.
DPFE TESTING RESULTS:
Engine running and hot, top wire = 2.84 volts
Engine off and cool (1hr cool down), key on, top wire = 2.71
Engine running and hot, bottom wire = 5.03 volts
Enine off and hot, key on, bottom wire = 5.03 volts

So I have test results but I am not sure of the wire locations. I think the bottom wire is my reference voltage and the top one is the signal. So if I get a 2+ volt reading when cold and never seem to get over a 2.85V reading when hot. The DPFE is not telling the PCM to open the EGR. Which with little change in voltage at any time would indicate a bad DPFE, right?

 

Hey, i finally saw what you replied in that other thread about the engine that dies, and was saying now that you have a 401 instead of a 402, and if it's a 4.6, you need to take the intake elbow off and clean the 2 egr holes out with a wide blade screwdriver. If you have any trouble, start a new thread with my name in it and i will keep a look out for you.....