I've got a P0401 on a 98 2.5 Automatic, - 4 Cylinder Gasoline - Ranger Engine Tech

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Posted: Sat Jul 20th, 2019 06:46 pm

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wh23g3g
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I've replaced all items on the egr system less than a year ago. I checked voltage on the DPFE and removed the whole vacuum harness to inspect for holes or cracks. I've replaced the DPFE sensor and vacuum solenoid under warranty, both Ford parts. The DPFE hoses are not clogged, they are fairly new and in good shape. The valve itself is a Ford valve less than a year old. I removed it and cleaned up in the intake but it wasn't clogged. I replaced the valve gasket. The P0401 comes back every time after about 10-15 miles. It doesn't run any different. Today I just checked the egr valve with a vacuum pump. I pumped it up and nothing changed at all. I've got a warranty valve and a new pipe. I was thinking maybe the pipe was clogged but I can't get the bottom nut to break loose so I quit trying. When I tested the valve with a vacuum pump I did it right away the first start of the day and also after driving a 50 mile round trip. Nothing happened when I applied vacuum to the valve and it didn't leak down. What does that mean?

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1998 Ford Ranger XLT 2.5 4R44E Automatic 4.10 non-limited slip, 1993 Ford Ranger XLT 2.3 M5 Manual, 3.45 non-limited slip

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Posted: Sat Jul 20th, 2019 11:53 pm

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if the valve did not pump up with vacuum it must have a hole in the diaphragm
Faulty EGR valve will cause excessing egr flow detected code
Which style EGR valve does your 2.5 use? Can you post a picture?
When you apply vacuum to the EGR valve it MUST open. If there is no change or it does not hold some vacuum there is a leak/hole inside the valve
I suspect bad egr valve new ford part or not

"Today I just checked the egr valve with a vacuum pump. I pumped it up and nothing changed at all"

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Posted: Sun Jul 21st, 2019 03:00 pm

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I got the Motorcraft CX1740 egr valve. I decided to change the EGR line and the new valve today. Well the SKP egr line did not fit quite right. It all appeared to have the same bends as the original one, except there was a slight bend on the original one near the exhaust manifold so I could not install the new EGR tube at all. I fought with the new EGR tube for almost two hours trying to get it to line up so I could tighten the tube nuts but it just wouldn't work. So I cleaned out the original one as best I could. I saw some carb on the inside walls of the tube but nothing clogged. It took about 5 minutes to get the original tube back on, no fighting with it at all. I went ahead and installed the warranty EGR valve. I checked the "faulty" EGR valve when I had it off with a vacuum pump. You could see the diaphragm arm moving so it did work somewhat I guess. Maybe there is something else wrong. Any I drove about 10 miles after clearing the code of course the P0401 came right back on. I don't know what else to do. I didn't use cheap parts, I checked the vacuum hoses, I checked the DPFE hoses, now I've cleaned the EGR tube out, both sensors, and now a new EGR valve have been installed within a couple of weeks. I sprayed out behind the EGR valve too while it was off but I didn't feel or see any high buildup of carbon. I'm assuming the EGR Solenoid fuse wouldn't be blown or otherwise I would be getting other codes. I just know when I had it running and pumped the EGR valve with the vacuum pump the engine didn't change at all. It's suppose to almost stall. It didn't do anything at all. The DPFE Volts PID is within specs at all ranges. I'm trying to get a brand new Jeep so hopefully this will be the last repair. But I'd like to have it fixed so I can sell it instead of using it as a trade in because I won't get anything on trade. What else could I check?

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1998 Ford Ranger XLT 2.5 4R44E Automatic 4.10 non-limited slip, 1993 Ford Ranger XLT 2.3 M5 Manual, 3.45 non-limited slip

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Posted: Mon Jul 22nd, 2019 11:55 am

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Dang that stinks! I hate codes that wont go away...
You said you replaced the DPFE, do you have your old one? Are these plastic or metal?

I hear you on the aftermarket EGR tube I have fought many a battle with those SOBS, but with pry bars, a vise, etc I can usually get them to thread. However you do not need a new EGR line if your factory one has no holes in it and you can clean it out

You do have the DPFE sample tubes routed properly? Large one on the large side, small on the other?
Having them backwards would cause a code. I have to ask.

You may need to do a manifold vacuum test, make sure your intake is making enough vacuum to open and close the valve. Do you have any vacuum leaks? PCV valve seated? Any torn rubber boots or split plastic lines? How is your idle?

I still suspect bad DPFE even though you replaced it, these things go out easily and I have seen my share of BAD ones
Any way to try and swap the DPFE with one from another engine? a known good one?

the P0401 code is insufficient flow detected...the DPFE is what does the "detecting" you have already confirmed you have good "flow"
Check the wiring coming into the DPFE, make sure the pins are good and clean and seated, the wires are in good shape, etc.

Last edited on Mon Jul 22nd, 2019 11:59 am by 410customs

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Posted: Mon Jul 22nd, 2019 09:17 pm

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I still have the DPFE. The one I replaced was Delphi and I replaced it with a new Motorcraft unit. The EGR solenoid was new Ford. I'm returning the EGR pipe because there's no way to get it on. I do have the DPFE hoses routed correctly, they are different sizes. I replaced them the last time I replaced the DPFE sensor so they still look new. The suggested symptom chart from Ford says that if there was no change in DPFE sensor reading when I pump the valve up with 10in-hg from a vacuum pump that their is a blockage. It said to remove the valve check it and check the manifold passage. I removed the valve, it still is new since I replaced it. I sprayed out the passageway some more with some cleaner. I also scraped out the passageway hole with a pick going all the way in until it bottom out. There was never any chunks of carbon but was some residue. So I reinstalled the valve and cleared the codes but haven't driven it enough to reset. I should know by tomorrow.

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1998 Ford Ranger XLT 2.5 4R44E Automatic 4.10 non-limited slip, 1993 Ford Ranger XLT 2.3 M5 Manual, 3.45 non-limited slip

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