Trying to get my 99 v-10 smogged. I have one code that keeps poping up after 15 miles, its po401 egr low flow . I have replaced the EGR valve, the dpfe selonoid, and pvc valve. what gives? smog guy says if you have any codes pending it won't pass. I even tried clearing the code and driving it 25 miles but the code comes up pending. this truck is very well maintained and has 53,000. what gives....thanks....Richard

 

Did you clean the throttle body passages where the EGR valve attaches to? There's usually all kinds of carbon in there which restricts gas flow to and from the EGR valve.

 

Ditto!! All the passages have to be clean. Also check the hoses going to the sensor...one big one small.

 

Thanks for the tip guys, I cant believe how much carbon is in there. I'm a motorcycle mechanic and we dont see this kind of carbon build up ever in bike engines,WOW ! ...Richard.

 

let me ask you this what Octane fuel you using ?
anything over 87 is a waste of money.
and will cause carbon build up .

keep your air cleaner changed more often also.

Rich

 

I ran a full tank of 91 once and it didnt seem to run any better,so I've been running 87 ever since. I've pulled the t-body off this weekend and cleaned every thing up. we'll see what happens when it all goes back together.

 

I still getting the same code coming up PO401. I cleaned the intake, replaced the four gaskets, there are two dpfe's if I am right. one is behind the t-bodie, theres another one on passenger side that has a diaphram and 2 hoses going into it, could this part be bad too ? I replaced every thing except the dpfe with the diaphram. funny thing is the truck runs better than ever. but the dam code comes on . should I replace the diaphram dpfe

 

Two hoses that come from the stainless pipe go to the sensor that measures flow through that pipe.Notice that the two pipes aren't the same size . That causes a pressure differential which can be measured....the other gizmo near the egr is a feedback valve which opens and closes the egr depending on engine load TPS angle and other stuff. If the egr doen't open there won't be any pressure to measure etc....There is a way to diagnose all this stuff but you can only guess. You need to have the manual and go through the steps to see which part is not working effectively.
Its quite complicated...

 

I would chk to see you have vacum to the egr valve , make sure of warm up time.
if you do then you know the egr vacum reg solenoid is working. if you don't then it could that or the voltage supplied from the pcm to operate it (you find it by following the vacum hose back from the egr valve itself)

Test your egr by appling vacum directly to it at idle if you apply vacum you could stall teh engine or at least lower the rpms.

As 99 said its manual time to get it all clear to you or the dreaded dealer trip.

Rich

 

Hello guy's,

I'm a new guy on the block. Like all of the info everyone imputs. I just had the SES light on and had the same code P0401 on my 99 v-10 with 93,000mi.(very pleased with the motor) Went and tested my EGR valve with one of the vacume pumps you can by at well, I would think at any autoparts store. EGR held vacume for more than 2 min with out a problem. Tried it with the engine running and it just about killed the motor from an idle meaning that the EGR valve itself is working properly. I thought I would replace it anyway so I ordered one at the local autoparts store. Then I called my local dealer to find out how to clear the error code on the PCM and he told me not to bother putting the valve on because he would almost garantee that is was the DPFE sensor, not the seloniod. He said that they probably replace 2-3 a day at the dealership. He also said that that Ford updated the replacement so it was much more durable. So I replaced the DPFE sensor(the part that 99f350sd is talking about in the above thread) instead of the EGR valve and sure enough I havent seen the SES light since. While I had the sensor off I sprayed a bit of brake cleaner down the rubber hoses that go to the stainless pipe out of the exhaust manifold to clean the carbon out. I do know that you have to have the code cleared by the dealer, (not sure if Autozone can?) on the newer OBD-II PCM's cause just disconecting the battery won' t work. Just thought I would imput my experience, I am glad I didn't waist the money on the valve, good luck, keep us posted.

 

Welcome Brad

I think if you disconnect the battery and turn the headlight sw on for 20 mins or so all codes will be lost....I'll have to read up on that but I think I'm right.

 

Disconnecting the battery for 5 mins will work.

I forgot to mention you can test the egr solenoid by taking a resistance chk across the 2 terminals
it should be between 20 -40 ohms.

Rich

 

Thanks for the correction 99f350sd, and thanks for the info FortyFords, I should have known not to take too much advise from the dealer. He told me that on the OBD-I PCM's that disconnecting the battery would work but not on the newer OBD-II's and that disconnecting the battery would work for a time on the OBD-II's but then the SES light would come on again cause the code wouldn't truely be cleared. He didn't charge me to clear the code though since I did the install of the DPFE sensor myself and drove right back to the dealer immediately to have it cleared. It's been off ever since though, I'm happy.

 

It finally passed the smog test. I took the dif presure valve off and blew it out with air. this was the problem all along. thanks for all your help guys.... . I orderd a new valve anyway. Nothing like having a good running truck with no check light popping up

 

Glad to see you passed the test. I've come to a conclusion, I hate sensors!!! I love my truck but man, my 77 F-250 still runs like a champ with no sensors at all. I don't have any complaints on the new pickup, it's been a real good vehicle with no other sensor problems. And I must say the new truck is quite a bit more efficient and not too crabby when it's cold outside. Nice to have fuel injection I guess. Ah yes, the good and bad points.