P0401 and P0402
Thread Starter
|
Junior Member
Joined: Apr 2008
Posts: 3
Likes: 0
P0401 and P0402
Truck: 2000, 5.4L v8, 4x4, 92,000 miles
Me: no engine expert, just what I read, so please bear with me
I know that there are several threads on these codes already, and I have read all of them, I think. I had a P0401 about 8 months ago, and replaced the metal-housed DPFE, which resolved the problem. Recently, P0401 came back and I took the TB apart to clean, as described in a few good step-by-step posts. To be honest, it did not seem all that dirty. Hoses all seem good; however, the two lines running into the DPFE seemed to have more buildup than anything. Cleaned, reassembled, cleared the code, and no sign of it for 5 days. Long enough to pass inspection, which was appreciated. Engine ran smooth, including at idle.
After 5 days, I could feel a rough idle at startup, and whenever I let off the gas while driving. By the time I had driven 13 miles to work under those conditions, the CEL was back on. Code is now P0402. So here are my questions:
If P0401 is insufficient, and P0402 is excessive, and the EGR valve controls how much exhaust gas is getting through, does this point to a faulty EGR valve? Maybe sticking closed, then open? Particularly with a new DPFE sensor already installed? Should I just replace the EGR valve and see? I cleared the code and it has not come back in one round-trip to work (26 miles), but the idle is rough.
Incidentally, this is my first F150, bought new exactly 8 years ago today. To-date, I have: replaced DPFE, 6 of 8 ignition coils, starter, entire transmission (warranty - woo-hoo!), and fixed a leaking back window (center-slide style, but the leak was in the corner behind driver seat). I also have the intermittent odometer "feature" and will use Greg Upton's excellent post to fix that some day when I have the time/inclination. This is a well-cared for truck, never been in an accident. Doesn't this seem excessive? Oh, and two years ago, the curved metal piece behind the cupholder that "springs" it out with a push, broke off! Now, if I accelerate hard, the darn cupholder slides out! Have not determined a fix for that yet. Sorry for the rant.
Me: no engine expert, just what I read, so please bear with me
I know that there are several threads on these codes already, and I have read all of them, I think. I had a P0401 about 8 months ago, and replaced the metal-housed DPFE, which resolved the problem. Recently, P0401 came back and I took the TB apart to clean, as described in a few good step-by-step posts. To be honest, it did not seem all that dirty. Hoses all seem good; however, the two lines running into the DPFE seemed to have more buildup than anything. Cleaned, reassembled, cleared the code, and no sign of it for 5 days. Long enough to pass inspection, which was appreciated. Engine ran smooth, including at idle.
After 5 days, I could feel a rough idle at startup, and whenever I let off the gas while driving. By the time I had driven 13 miles to work under those conditions, the CEL was back on. Code is now P0402. So here are my questions:
If P0401 is insufficient, and P0402 is excessive, and the EGR valve controls how much exhaust gas is getting through, does this point to a faulty EGR valve? Maybe sticking closed, then open? Particularly with a new DPFE sensor already installed? Should I just replace the EGR valve and see? I cleared the code and it has not come back in one round-trip to work (26 miles), but the idle is rough.
Incidentally, this is my first F150, bought new exactly 8 years ago today. To-date, I have: replaced DPFE, 6 of 8 ignition coils, starter, entire transmission (warranty - woo-hoo!), and fixed a leaking back window (center-slide style, but the leak was in the corner behind driver seat). I also have the intermittent odometer "feature" and will use Greg Upton's excellent post to fix that some day when I have the time/inclination. This is a well-cared for truck, never been in an accident. Doesn't this seem excessive? Oh, and two years ago, the curved metal piece behind the cupholder that "springs" it out with a push, broke off! Now, if I accelerate hard, the darn cupholder slides out! Have not determined a fix for that yet. Sorry for the rant.
Senior Member
Joined: Dec 2006
Posts: 43,542
Likes: 819
From: Joplin MO
If you did not buy the DPFE from the Ford dealer, there's a very good chance it's bad.
Pull the vacuum hose off the EGR valve at idle and stick your thumb over it to feel for vacuum. If there is vacuum, something is wrong in the control circuit and the idle should smooth out when you do this, there should not be any vacuum.
If there's no vacuum, then take a spare piece of vacuum hose and connect it to the EGR valve and suck on it like a straw. The idle should drop and get rough, if not, the EGR valve itself is bad.
Pull the vacuum hose off the EGR valve at idle and stick your thumb over it to feel for vacuum. If there is vacuum, something is wrong in the control circuit and the idle should smooth out when you do this, there should not be any vacuum.
If there's no vacuum, then take a spare piece of vacuum hose and connect it to the EGR valve and suck on it like a straw. The idle should drop and get rough, if not, the EGR valve itself is bad.
Senior Member
Joined: Aug 2007
Posts: 151
Likes: 0
From: Southaven, MS
Truck: 2000, 5.4L v8, 4x4, 92,000 miles
Me: no engine expert, just what I read, so please bear with me
I know that there are several threads on these codes already, and I have read all of them, I think. I had a P0401 about 8 months ago, and replaced the metal-housed DPFE, which resolved the problem. Recently, P0401 came back and I took the TB apart to clean, as described in a few good step-by-step posts. To be honest, it did not seem all that dirty. Hoses all seem good; however, the two lines running into the DPFE seemed to have more buildup than anything. Cleaned, reassembled, cleared the code, and no sign of it for 5 days. Long enough to pass inspection, which was appreciated. Engine ran smooth, including at idle.
After 5 days, I could feel a rough idle at startup, and whenever I let off the gas while driving. By the time I had driven 13 miles to work under those conditions, the CEL was back on. Code is now P0402. So here are my questions:
If P0401 is insufficient, and P0402 is excessive, and the EGR valve controls how much exhaust gas is getting through, does this point to a faulty EGR valve? Maybe sticking closed, then open? Particularly with a new DPFE sensor already installed? Should I just replace the EGR valve and see? I cleared the code and it has not come back in one round-trip to work (26 miles), but the idle is rough.
Incidentally, this is my first F150, bought new exactly 8 years ago today. To-date, I have: replaced DPFE, 6 of 8 ignition coils, starter, entire transmission (warranty - woo-hoo!), and fixed a leaking back window (center-slide style, but the leak was in the corner behind driver seat). I also have the intermittent odometer "feature" and will use Greg Upton's excellent post to fix that some day when I have the time/inclination. This is a well-cared for truck, never been in an accident. Doesn't this seem excessive? Oh, and two years ago, the curved metal piece behind the cupholder that "springs" it out with a push, broke off! Now, if I accelerate hard, the darn cupholder slides out! Have not determined a fix for that yet. Sorry for the rant.
Me: no engine expert, just what I read, so please bear with me
I know that there are several threads on these codes already, and I have read all of them, I think. I had a P0401 about 8 months ago, and replaced the metal-housed DPFE, which resolved the problem. Recently, P0401 came back and I took the TB apart to clean, as described in a few good step-by-step posts. To be honest, it did not seem all that dirty. Hoses all seem good; however, the two lines running into the DPFE seemed to have more buildup than anything. Cleaned, reassembled, cleared the code, and no sign of it for 5 days. Long enough to pass inspection, which was appreciated. Engine ran smooth, including at idle.
After 5 days, I could feel a rough idle at startup, and whenever I let off the gas while driving. By the time I had driven 13 miles to work under those conditions, the CEL was back on. Code is now P0402. So here are my questions:
If P0401 is insufficient, and P0402 is excessive, and the EGR valve controls how much exhaust gas is getting through, does this point to a faulty EGR valve? Maybe sticking closed, then open? Particularly with a new DPFE sensor already installed? Should I just replace the EGR valve and see? I cleared the code and it has not come back in one round-trip to work (26 miles), but the idle is rough.
Incidentally, this is my first F150, bought new exactly 8 years ago today. To-date, I have: replaced DPFE, 6 of 8 ignition coils, starter, entire transmission (warranty - woo-hoo!), and fixed a leaking back window (center-slide style, but the leak was in the corner behind driver seat). I also have the intermittent odometer "feature" and will use Greg Upton's excellent post to fix that some day when I have the time/inclination. This is a well-cared for truck, never been in an accident. Doesn't this seem excessive? Oh, and two years ago, the curved metal piece behind the cupholder that "springs" it out with a push, broke off! Now, if I accelerate hard, the darn cupholder slides out! Have not determined a fix for that yet. Sorry for the rant.
EDIT: My P0401 fix was very simple....since I have the 4.6L, the DPFE sensor isn't located in the same place as yours, and its plastic stock....one of the hoses on the sensor...the insides of it were shreaded and clogged up the line!! $26 from autozone and a new piece of hose, fixed!
Last edited by jetlag; Apr 12, 2008 at 03:01 AM.
Junior Member
Joined: Nov 2007
Posts: 4
Likes: 0
From: Abilene, TX
I was getting the same P0401 code and changed everything except the EGR valve and what it ended up being was the passage in the throttle body was getting clogged up by carbon deposits, so first and foremost you need to pull the throttle body off and clean out the passage. There's a plug in the passage that you can remove with an allen/hex head wrench to clean the passage easier, just make sure you count the number of turns it took to get it out so you put it back in the same position. So far I've gone almost a week without getting the code back. Good luck.
Thread Starter
|
Junior Member
Joined: Apr 2008
Posts: 3
Likes: 0
Just an update on the resolution:
I gave myself until Memorial weekend to fix this myself, but never found the time. So I took it into my mechanic who diagnosed the problem as leaky gaskets. Took it all apart, replaced worn gaskets, cleaned it all up, and everything is running smoothly. No new parts other than gaskets - no DPFE (which I had already replaced last year), EGR valve, sensor, etc.
He said general maintenance. Paid for some labor, but worth it!
I gave myself until Memorial weekend to fix this myself, but never found the time. So I took it into my mechanic who diagnosed the problem as leaky gaskets. Took it all apart, replaced worn gaskets, cleaned it all up, and everything is running smoothly. No new parts other than gaskets - no DPFE (which I had already replaced last year), EGR valve, sensor, etc.
He said general maintenance. Paid for some labor, but worth it!
Technical Article Contributor
Joined: Oct 2005
Posts: 25,641
Likes: 19
From: MI
It takes 3 or 4 good drive cycles to know if the 401-402's are indeed fixed. The PCM has to fail flow tests 3 times before an engine light illuminates. 402 is a poppet valve/diaphragm problem generally , unless of course you have leaks which isn't to often. The ONLY gasket that could cause that code is the EGR to TB gasket which is aluminum. I've used mine over and over again repeatedly for 240,000 miles - that one doesn't ware out. It may have been damaged during assembly or maybe it wasen't cleaned good, that's about it.
If you did truly read ALL posts then you would have suck tested the diaphragm. That's been posted many times / procedure and why with illustrations.
If you did truly read ALL posts then you would have suck tested the diaphragm. That's been posted many times / procedure and why with illustrations.
Last edited by jbrew; Jun 2, 2008 at 06:08 PM.
Junior Member
Joined: Dec 2010
Posts: 1
Likes: 0
Fix to the cup holder.
Truck: 2000, 5.4L v8, 4x4, 92,000 miles
Me: no engine expert, just what I read, so please bear with me
I know that there are several threads on these codes already, and I have read all of them, I think. I had a P0401 about 8 months ago, and replaced the metal-housed DPFE, which resolved the problem. Recently, P0401 came back and I took the TB apart to clean, as described in a few good step-by-step posts. To be honest, it did not seem all that dirty. Hoses all seem good; however, the two lines running into the DPFE seemed to have more buildup than anything. Cleaned, reassembled, cleared the code, and no sign of it for 5 days. Long enough to pass inspection, which was appreciated. Engine ran smooth, including at idle.
After 5 days, I could feel a rough idle at startup, and whenever I let off the gas while driving. By the time I had driven 13 miles to work under those conditions, the CEL was back on. Code is now P0402. So here are my questions:
If P0401 is insufficient, and P0402 is excessive, and the EGR valve controls how much exhaust gas is getting through, does this point to a faulty EGR valve? Maybe sticking closed, then open? Particularly with a new DPFE sensor already installed? Should I just replace the EGR valve and see? I cleared the code and it has not come back in one round-trip to work (26 miles), but the idle is rough.
Incidentally, this is my first F150, bought new exactly 8 years ago today. To-date, I have: replaced DPFE, 6 of 8 ignition coils, starter, entire transmission (warranty - woo-hoo!), and fixed a leaking back window (center-slide style, but the leak was in the corner behind driver seat). I also have the intermittent odometer "feature" and will use Greg Upton's excellent post to fix that some day when I have the time/inclination. This is a well-cared for truck, never been in an accident. Doesn't this seem excessive? Oh, and two years ago, the curved metal piece behind the cupholder that "springs" it out with a push, broke off! Now, if I accelerate hard, the darn cupholder slides out! Have not determined a fix for that yet. Sorry for the rant.
Me: no engine expert, just what I read, so please bear with me
I know that there are several threads on these codes already, and I have read all of them, I think. I had a P0401 about 8 months ago, and replaced the metal-housed DPFE, which resolved the problem. Recently, P0401 came back and I took the TB apart to clean, as described in a few good step-by-step posts. To be honest, it did not seem all that dirty. Hoses all seem good; however, the two lines running into the DPFE seemed to have more buildup than anything. Cleaned, reassembled, cleared the code, and no sign of it for 5 days. Long enough to pass inspection, which was appreciated. Engine ran smooth, including at idle.
After 5 days, I could feel a rough idle at startup, and whenever I let off the gas while driving. By the time I had driven 13 miles to work under those conditions, the CEL was back on. Code is now P0402. So here are my questions:
If P0401 is insufficient, and P0402 is excessive, and the EGR valve controls how much exhaust gas is getting through, does this point to a faulty EGR valve? Maybe sticking closed, then open? Particularly with a new DPFE sensor already installed? Should I just replace the EGR valve and see? I cleared the code and it has not come back in one round-trip to work (26 miles), but the idle is rough.
Incidentally, this is my first F150, bought new exactly 8 years ago today. To-date, I have: replaced DPFE, 6 of 8 ignition coils, starter, entire transmission (warranty - woo-hoo!), and fixed a leaking back window (center-slide style, but the leak was in the corner behind driver seat). I also have the intermittent odometer "feature" and will use Greg Upton's excellent post to fix that some day when I have the time/inclination. This is a well-cared for truck, never been in an accident. Doesn't this seem excessive? Oh, and two years ago, the curved metal piece behind the cupholder that "springs" it out with a push, broke off! Now, if I accelerate hard, the darn cupholder slides out! Have not determined a fix for that yet. Sorry for the rant.
I just took the ash tray out and used 2 small screws where the holes go to fix the cup holder spring. No kind of glue will work.
Trending Topics
Thread Starter
|
Junior Member
Joined: Apr 2008
Posts: 3
Likes: 0
cameroncobb: Wow! Two and half years later! I still have the truck, and still have done nothing to fix the ash tray, but I'm inspired now. Thanks for responding!