[FIXED] 2001 Ford F150 P0401 code

All right so I watched the video and looked at the wiring diagram from tyler. So yes it is from ground to brown/pink wire. I made a cable jumper and put my voltmeter at the DPFE top wire to monitor the voltage. With KOER I have 1.02v at idle. When I apply the jumper cable to the brown/pink wire the engine idles a little rough and the voltage only goes up to 1.27v. Even if I accelerate a little with the jumper wire is in place the voltage won't go higher than 1.27v. So the test didn't work before due to and LED test light.

So it appears that even if the PCM send the ground signal to solenoid it is not the issue as the voltage situation remains. What you do you think?

jayta98 wrote: So if I'm going to use a jumper wire to test the EVR test like showed in the video I'm going to use the jumper wire from battery ground to the brown/pink wire I should see the engine stall a little and the DPFE voltage should increase, correct? I just want to make sure I don't fry my PCM when using the jumper wire. So from battery ground to brown/pink wire? Sorry to ask twice but i want to make sure.

No problem - always good to be double sure on this kind of stuff. Yep, B- to the brown/pink wire should either stall the engine, or close to it.

Actually, in this situation, you still can't fry the PCM driver, even if you connected to the wrong EVR wire. The only way you could let the smoke out of the PCM would be if you connected the jumper to B+, or if you had the backprobe installed crooked enough that it was touching both pins.

Thanks everyone for stepping in and help. I have this problem for about a year now. I will like to resolve it.

Thank YOU for sticking with us! We want to see this one fixed.

Tyler wrote:

jayta98 wrote: So if I'm going to use a jumper wire to test the EVR test like showed in the video I'm going to use the jumper wire from battery ground to the brown/pink wire I should see the engine stall a little and the DPFE voltage should increase, correct? I just want to make sure I don't fry my PCM when using the jumper wire. So from battery ground to brown/pink wire? Sorry to ask twice but i want to make sure.

No problem - always good to be double sure on this kind of stuff. Yep, B- to the brown/pink wire should either stall the engine, or close to it.

Actually, in this situation, you still can't fry the PCM driver, even if you connected to the wrong EVR wire. The only way you could let the smoke out of the PCM would be if you connected the jumper to B+, or if you had the backprobe installed crooked enough that it was touching both pins.

Thanks everyone for stepping in and help. I have this problem for about a year now. I will like to resolve it.

Thank YOU for sticking with us! We want to see this one fixed.

One thing i have noticed is that even if I apply vacuum to the EGR directly or even when i did the EVR test the engine will idle slightly rough. I mean it is no were near stall or ever had stall. Not sure if that detail helps out.

Another thing that comes to my mind is the EGR tube. I did pulled the tube out and checked it for obstructions yesterday. Well to my understanding there is supposed to be an orifice in there between the two ports for the DPFE hoses. I remembered when I blew in the EGR opening( the tube itself) I didn't felt any resistance like the tube orifice was as big as the tube. Im not sure the size of this orifice but if it is supposed to be very small then i should feel some resistance when i blew into it. I pulled the DPFE hoses of the sensor when the engine was running at idle and I feel a very small amount of pulsating air from each hose.

Does that sounds about the right amount of air pressure? I never checked the manifold hole itself for obstruction when I removed the pipe. I can take it off again tomorrow. I can start the truck and feel the exhaust pressure coming out of it.

Well i haven't heard any more suggestions and i dont have any new updates. At this point i either learn to live with the ses light or take it to the dealership close by. I know is emission related and we dont have inspections in florida but i think this is a affecting my gas mileage. I have tried everything possible but it doesnt make sense.

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Hey jayta98! Didn't mean to leave you hanging... I was actually waiting to hear back about the EVR test. Did you get a result by applying a jumper wire to the EVR solenoid?

Does that sounds about the right amount of air pressure? I never checked the manifold hole itself for obstruction when I removed the pipe. I can take it off again tomorrow. I can start the truck and feel the exhaust pressure coming out of it.

I'm honestly not sure. :dry: I've never had one of those pipes off, so I can't say with confidence what kind of pressure you should feel. To me, if you can feel exhaust pulses at the main EGR valve connection and both the DPFE hose ports, then I think you're good.

Tyler wrote: Hey jayta98! Didn't mean to leave you hanging... I was actually waiting to hear back about the EVR test. Did you get a result by applying a jumper wire to the EVR solenoid?

Does that sounds about the right amount of air pressure? I never checked the manifold hole itself for obstruction when I removed the pipe. I can take it off again tomorrow. I can start the truck and feel the exhaust pressure coming out of it.

I'm honestly not sure. :dry: I've never had one of those pipes off, so I can't say with confidence what kind of pressure you should feel. To me, if you can feel exhaust pulses at the main EGR valve connection and both the DPFE hose ports, then I think you're good.

i posted the results earlier. With the actual jumper to the solenoid the engine idles a little rough but it never stalls or dies. The voltage at dpfe is still around 1.27v. So no change there. Even if it is vacuum related i think i would have the right results when i use the vacuum pump directly on the egr valve. I get the same results and engine rough idle and no change on voltage.

Somethings isn't right here! I didnt read through all the posts so forgive me if this has already been done but If you can't stall an engine with the egr than it's either not opening all the way or either the tube or intake is plugged id start with pulling the egr apply vacuum (make sure it holds vacuum and opens fully) clean the intake port while it's off. The pipe can be more tricky but if it's neither of those than we'll look at pipe

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I don't even bother with dpfe voltages till egr is working correct.

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Ben wrote: Somethings isn't right here! I didnt read through all the posts so forgive me if this has already been done but If you can't stall an engine with the egr than it's either not opening all the way or either the tube or intake is plugged id start with pulling the egr apply vacuum (make sure it holds vacuum and opens fully) clean the intake port while it's off. The pipe can be more tricky but if it's neither of those than we'll look at pipe

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yes the tb is clean and clear. The egr was pulled and i manually applied vacuum. It can see internal piston moving and creating a 1/4 inch opening. The vacuum holds which tells me the diaphragm is intact. I agree it could be the tube. The only replacement is the dorman one and it seems from the reviews is not a perfect fit and needs to be modified to fit. The tube is very clear when i blow air thru it. I mean lile there is not an obstruction so i guess it could be the egr then? But it appears to be fully open.

Ben wrote: Somethings isn't right here!

Exactly what I've been thinking the whole time! :lol: I'm pretty sure there's a genuine low flow issue at this point, but I can't decide if it's something in the EGR pipe, or if it's the EGR valve.

With the actual jumper to the solenoid the engine idles a little rough but it never stalls or dies. The voltage at dpfe is still around 1.27v. So no change there.

Good stuff, sorry I missed that earlier! :blush: This is what makes me believe in a low flow issue, as I've done this test many times on known good vehicles, and always got them to flat-out stall.

I wanna say EGR? But I don't wanna be that guy that guesses on parts. :lol:

Tyler wrote:

Ben wrote: Somethings isn't right here!

Exactly what I've been thinking the whole time! :lol: I'm pretty sure there's a genuine low flow issue at this point, but I can't decide if it's something in the EGR pipe, or if it's the EGR valve.

With the actual jumper to the solenoid the engine idles a little rough but it never stalls or dies. The voltage at dpfe is still around 1.27v. So no change there.

Good stuff, sorry I missed that earlier! :blush: This is what makes me believe in a low flow issue, as I've done this test many times on known good vehicles, and always got them to flat-out stall.

I wanna say EGR? But I don't wanna be that guy that guesses on parts. :lol:

i ordered the egr valve and i will try it out. I think the current one it was a generic model so i went with motorcraft one this time. I also have a small usb endoscope camera. Im going to pull the egr tube out again and see if the tiny camera fits inside and i can look at the orifice to confirm is not obstructed.

If you are telling me that i should be able to stall the engine out with the jumper to the solenoid or by applying vacuum to the egr then it obvious there is not enough flow. I know there is no obstruction on the throttle body. i pulled the tube before and started the truck to feel for air flow at the manifold hole and i felt plenty of it. Once i get the egr valve on Wednesday is will update my findings.

All right everyone here is the update. So I ordered the EGR but this time the motorcraft brand. I can tell that right of the bad the EGR opening once I put vacuum in is bigger. On the process of removing the bracket containing the dpfe sensor and eVR solenoid I broke off on eof the ports of the dpfe sensor. So I ordered a new dpfe sensor and a EGR tube replacement just in case. Once all the parts were here I tried installing the EGR tube 1st with the old EGR. No change when I use the jumper on the EVR solenoid test. I took off the EGR tube and let me tell you the dorman replacement is a pain to install. The tube is not shaped exactly the same. A lot of the reviews that I found mentioned the same.

Next I installed the new motorcraft EGR and tried the EVR solenoid jumper test. Immediately the engine idle really bad and it stalled. Now that is what you guys told me it should happen so I knew EGR flow was good this time. I installed the new DPFE sensor and put everything back. KOER i put my voltmeter on the DPFE and applied vacuum to the EGR. This time it did what it should do. The engine started to idle real bad as i applied vacuum and the DPFE sensor voltage went up from 1.02v to 3.5v and higher with the more vacuum I applied.

So after all it was the non motorcraft EGR valve. I bought the aftermarket EGR valve and installed it about 1 year ago. The valve was not the right one for the truck and it started causing the issues. I'm not buying Ford engine parts that are not OEM brand anymore. It has not been the 1st time I had issues with aftermarket parts on Fords.

I cleared the codes and so far I drove the truck 3 times and no SES light. I'm pretty sure i got it. I removed the dorman EGR tube and installed the factory one. Same voltage results and the engine stalls with the EVR test. I'm returning the tube back since it is a bad fit.

I want to thank all of you that pointed me in the right direction and took their time answer my questions. It's a long time with that SES light on my cluster.

Now I have to do some suspension work. It never ends. Juan.

YESSSSSS! :woohoo: That's fantastic! Truly excited to hear this, Juan - we've been chasing this one for a month. :ohmy:

I bought the aftermarket EGR valve and installed it about 1 year ago. The valve was not the right one for the truck and it started causing the issues. I'm not buying Ford engine parts that are not OEM brand anymore. It has not been the 1st time I had issues with aftermarket parts on Fords.

Ah hah! :lol: I wonder which truck it was designed for, then? Also been down that road with aftermarket parts. I've got two Fords in my family now, and both get Motorcraft stuff whenever possible. As the saying goes, the cheap part may be cheaper, but not necessarily less expensive. :lol: Of course, in this case, the aftermarket EGR might have been misboxed? Or someone at the parts store grabbed the wrong one off the shelf?

Hello again. I just wanted to report back that I still have no SES light It is nice to not see it anymore. Thanks guys i couldn't got it done without this forum.

Good work glad you got it figured out it whenever you have 1 that won't stall an engine it's a flow problem either a plugged tube or in this case the egr valve is restricting flow

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Ben wrote: Good work glad you got it figured out it whenever you have 1 that won't stall an engine it's a flow problem either a plugged tube or in this case the egr valve is restricting flow

Ben is absolutely right - this is where I went wrong initially. :blush: I knew a wide open EGR should generate a stall, but I let it go because I have seen a couple that didn't stall but still passed their EGR monitor. Shoulda listened to my gut on that one.