DTC P0401?
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Senior User
Joined: Aug 2006
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From: San Mateo
DTC P0401?
Help!
I got this DTC on my truck. P0401.
I have really noticed my fuel milage going down.
I recently got my truck tuned up, spark plugs, wires, cap and rotor etc, about a week ago, but now I am getting this dang code.
Any help much appreciated.
I got this DTC on my truck. P0401.
I have really noticed my fuel milage going down.
I recently got my truck tuned up, spark plugs, wires, cap and rotor etc, about a week ago, but now I am getting this dang code.
Any help much appreciated.
Senior User
Joined: May 2009
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From: Moyock
defintely an egr problem, my truck is having the same code. and suffering the mpg loss and idle issues. something is either pulling a vacuum on your EGR valve at idle or the EGR valve is stuck. i would try removing the vacuum line on top of the EGR and see if your idle issues go away.
these two codes are what i have..
P0401-EGR insufficiant flow
P0402-EGR excessive flow
i have tryed changing the EGR solenoid 3 times with my donor trucks, no luck... i am about convinced its the EGR valve. but first you could try changing this solenoid, it is located in front of the coil on top of the engine with 2 vacuum lines and a 2 wire plug connected to it..
if that doesnt work you could also try removing the EGR valve and inspecting it for major carbon build and try cleaning it... still hasnt worked for me but its worth a try
these two codes are what i have..
P0401-EGR insufficiant flow
P0402-EGR excessive flow
i have tryed changing the EGR solenoid 3 times with my donor trucks, no luck... i am about convinced its the EGR valve. but first you could try changing this solenoid, it is located in front of the coil on top of the engine with 2 vacuum lines and a 2 wire plug connected to it..
if that doesnt work you could also try removing the EGR valve and inspecting it for major carbon build and try cleaning it... still hasnt worked for me but its worth a try
Fleet Owner
Joined: Oct 2005
Posts: 20,789
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From: Kentucky
The '96 and later trucks using OBD-II use different EGR sensing from the earlier OBD-I trucks. OBD-II now measures the EGR flow via a DPFE (Differential Pressure Feedback) sensor. It is the pressure drop between two orifices in the EGR line that is measured. The DPFE sensor itself is remote mounted from the EGR/EGR Line. There are two silicone hoses running between the DPFE and the EGR line.
The most common cause of this error is carbon build up in the EGR line as well as on the EGR pintle seat. The silicone lines can also crack over time. The EGR line itself can develop cracks as well. The original Ford design was not the greatest in the world. The service replacement no longer has the accordion style flexible section. The last item on the list is the DPFE sensor.
I snagged a testing procedure from a previous post on this subject: FORD DPFE SENSOR TEST
The most common cause of this error is carbon build up in the EGR line as well as on the EGR pintle seat. The silicone lines can also crack over time. The EGR line itself can develop cracks as well. The original Ford design was not the greatest in the world. The service replacement no longer has the accordion style flexible section. The last item on the list is the DPFE sensor.
I snagged a testing procedure from a previous post on this subject: FORD DPFE SENSOR TEST
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Joined: Jan 2011
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I also got this code on my van. I did get some responses from it on the thread I started. I would just like to know if I can use my AutoXRay 6000 scan tool, on 'data streaming' mode, to see what it is, exactly. The other members are saying it's either the EGR valve, or the DPFE sensor.
John
John
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Fleet Owner
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From: Kentucky
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Does the CEL come on when the P0401 code is present (in a '96 F-150 w/ OBD-II)? Reason I ask is my truck failed inspection with that code but CEL was not on, and the guy said someone removed the bulb. 
Before I go after the seller, I want to verify this. Is there an easy way to check if the bulb is there without taking the dash apart?
Before I go after the seller, I want to verify this. Is there an easy way to check if the bulb is there without taking the dash apart?
Junior User
Joined: Mar 2011
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Thanks, rla2005, it doesn't come on at all, I know what you mean. So it would appear either the bulb's burned out, fuse/wiring problem or someone removed the bulb, right? I'd still like to know which.
Bottom line, looks like I gotta replace the bulb either way, so from what little I understand reading this forum, etc., I'll have to remove the cluster or take it to a mechanic, as well as deal with the P0401 code. Any advice for a n00b welcome, thanks.
Bottom line, looks like I gotta replace the bulb either way, so from what little I understand reading this forum, etc., I'll have to remove the cluster or take it to a mechanic, as well as deal with the P0401 code. Any advice for a n00b welcome, thanks.
Fleet Owner
Joined: Oct 2005
Posts: 20,789
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From: Kentucky
The dash comes apart pretty easily. You can use this to see how the dash cover comes off, then you can pull out the cluster to replace the bulb(s): Dash pad replacement, 92-96 - FSB Forums
Your code P0401 is not that tough to fix either. Usually the silicone hoses can crack with age. This skews the pressure readings which in turn cause the P0401 error. The EGR tube can also plug up with carbon or worse yet it can develop small cracks. A good visual check is in order here before tossing in the towel.
I have used this DPFE sensor test procedure a few times as well: FORD DPFE SENSOR TEST
Your code P0401 is not that tough to fix either. Usually the silicone hoses can crack with age. This skews the pressure readings which in turn cause the P0401 error. The EGR tube can also plug up with carbon or worse yet it can develop small cracks. A good visual check is in order here before tossing in the towel.
I have used this DPFE sensor test procedure a few times as well: FORD DPFE SENSOR TEST
Junior User
Joined: Mar 2011
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So far, it's going pretty well. Had some trouble getting the headlight **** out, then the whole thing came out. Oops.
BTW, was I supposed to disconnect the battery first? Cuz, well, I didn't.
I got the bezel off fairly easily after that, except the left wire harness was pretty stubborn.
I then removed the 4 bolts holding the cluster. I was able to tilt it back and get at the bulbs without disconnecting the cluster from the wire harnesses.
I found one burned out bulb behind the CEL, so there's the answer.
Think I'll replace all of them while I'm at it.
Anything else I should do before I put it back together?
Next, I'll need to get into the P0401 issue. I'll try the DPFE sensor test.
BTW, was I supposed to disconnect the battery first? Cuz, well, I didn't.
I got the bezel off fairly easily after that, except the left wire harness was pretty stubborn.
I then removed the 4 bolts holding the cluster. I was able to tilt it back and get at the bulbs without disconnecting the cluster from the wire harnesses.
I found one burned out bulb behind the CEL, so there's the answer.
Think I'll replace all of them while I'm at it. Anything else I should do before I put it back together?
Next, I'll need to get into the P0401 issue. I'll try the DPFE sensor test.