P0401 won't go away!

[scruffy1]

Just bought this truck. 2001 Ranger, 3.0.
Previous owner said EGR code came on with him and he replaced the EGR valve and the DPF sensor. I had in one day and the CEL came on and threw the P0401 code. Have replaced the egr solenoid, cleaned the throttle body, cleaned the EGR tube and port from the EGR valve. ERR works fine with suction applied. VERY frustrated. I found reference to a TSB#0361 and 0322 that is supposed to address this very problem. Anybody know anything about this?

Thanks.

 

[bikerboy]

did you cleaning the hoses at the dpfe? try cleaning them out and letting the hoses off over night and let them dry. clear the code and try again.

 

[scruffy1]

Yes, I cleaned the EGR tube and the rubber lines running to the DPF. Just pulled the lines again and blew air through both and they are clear. Is there something "upstream" that could be causing this?

 

[scruffy1]

I had taken the EGR tube off earlier and cleaned it along with the DPFE ports. I noticed on a schematic that the EGR tube has an orifice between the two DPFE feed tubes so I removed it again and ran a wire through it along with a bunch of solvent. I'll know tomorrow if this did the trick. I've also cleared the code many times now, starting to wonder if you can clear it too many times

 

[sam]

I recently had a similar problem with a 3.0L in a 94 B3000. I didn't replace anything except the DPFE mainly because the engine had 211,xxx miles on it. What I discovered after searches on this board and testing was that the intake was so curdded up with carbon that no exhaust gas flowed at all when the computer told it (the EGR valve) to open. With no EGR flow, the DPFE can't detect a differential pressure, thus the computer throws a code.

I don't know if you have a code reader (I do and its an EEC IV system), but you can do a Key on engine running test while monitoring the vacuum line to the EGR which will tell you that all the controls work if the vacuum goes to something like 7 inches. That pointed to EGR flow blockage for me. I pulled the EGR valve and could actually run the engine with no performance issues at all.

Simple test for this would be to pull the EGR vale, or pull the tube and hook up a mighty vac to the EGR vacuum line and open it then start the engine. You can easily tell if the passage is blocked because there will be little to no flow detected and the engine will run bad. I put a rag ovet the exhaust tube go muffle the sound.

Good luck, this worked for me. If it's blocked, your going to have fun opening it up. I pulled big chuncks of crap from the intake using an assortment of things like picks, wire brushes, rifle cleaning kit, coat hangers, screwdrivers, etc. You can't see the passage, and it isn't a stratght shot, so just keep at it. When it's open, you will know.

Sam

 

[scruffy1]

thanks Sam.

I'm starting to think it may be a vacuum problem. All the ports are cleaned, the egr tube has been removed twice and cleaned. All control units have been replaced. I'll put together a vacuum setup and check it out as you suggested. I did notice what looked like two very small pin holes in a plastic vacuum line between the head and the firewall (running from the egr solenoid to the egr valve. Looks like someone may have thought the line was an electrical line and stuck a probe in it. I'll start there.
Interesting note. Twice now when I have cleared the codes, let the computer relearn idle,etc. Then took it on the highway for a 20 mile run at highway speeds the light stays off. I'll park it for the night and the next day it comes on almost immediately after begining driving.

 

[scruffy1]

As an experiment I cleared the code and took the truck out on the highway. I traveled 60 miles to the work site, used the truck to do some log drags (which amounted to maybe 30 minutes of run time) and the light stayed off. The truck was used off and on all day.

Got in the truck to drive the 60 miles home and within 5 miles of non-highway speeds the CEL comes back on. Gas mileage seems OK, truck runs fine.

Any clues???

I'm thinking about taking the truck down for an emissons test to see if the EGR system actually is malfunctioning.

 

[scruffy1]

Finally got the damn light to go off and it was a simple fix that made me feel like an idiot.
It was the DPFE sensor! The previous owner had told me he replaced the sensor so I took that for face value and did all the time wasting work mentioned in my previous posts. In desperation I finally went to the parts store and put the money down for a new DPFE (non-refundable purchase, by the way), traded out the "new" one that came with the truck and have been running CEL free ever since.
The new sensor looked the same as the old one but was a bit thicker front to back.
So, I'm thinking the previous owner:

1. Replaced the sensor with the wrong one, if you can do such a thing.
2. Lied to me about replacing it since it is kind of pricey, imagine that, a seller lying to a potential buyer.
3. Actually did replace the sensor and it failed.

Regardless, I am now intimate with my EGR system and can drive without that light staring at me. I guess it's the small things in life.

Thanks for all your input.

 

[97ranger4x4]

I just got the same code on my 4.0 Looks like I will start looking around to see what I can do to get this fixed.

 

[bikerboy]

Post the exact code here as well as all truck info. Year make model engine 4x4 or 4x2. auto or manual. edge or any other special label. and I can help you out.

 

[97ranger4x4]

I have the P0401 code. My truck is in my signature but its a 97 4.0 XLT 4x4 w/ an automatic.

from doing some research online it looks like the DPFE sees a lot of water and many other harsh environments. Looks like most people recommend taking it off, and letting it dry out. I saw online there was a way to the sensor out with a meter. So I will check it out when I get a chance this weekend.

Also all of my vacume lines are a year old. So they are in good shape and no rotting.

The only issues I have when it runs is when I start it up, It takes a little longer than ususal to crank over. And then it idles a little over 1000 for about 20-30 seconds (nothing abnormal), but then it drops down almost to the point of shutting off. Then it jumps back up to 1000 rpms where it sits until it warms up. By the time its at full opperating temp. it has a smooth idle and no other issues.

Thanks for your help.

Keith

 

[bikerboy]

Here you go. Run this test and post back with your results. Thanks and hope it works!

1. Check the voltage of the Differential Pressure Feedback EGR (DPFE) sensor on the scan tool or on the Brown/Light Green (BR/LG) wire at the DPFE sensor connection. The circuit should indicate 0.5-1.2 volts Key On, Engine Off (KOEO) or at idle with the sensor connected.
2. If the sensor voltage does not read within the proper range, disconnect the sensor and re-check the voltage on the scan tool or BR/LG wire. Voltage should indicate 5.0 volts with the sensor unplugged.
3. Check voltage between the Brown/White (BR/W) wire and the Grey/Red (GY/R) wire. Voltage should indicate 5 volts with the sensor connected or not.
4. If the voltage of the DPFE sensor responds after it is disconnected and 5.0 volts is present between the other two circuits on the sensor, replace the DPFE sensor.
5. If the voltage in step 1 is measured to be correct, disconnect the Exhaust Gas Recirculation (EGR) vacuum line and open the EGR valve with a hand-held vacuum pump when the engine is idling. The engine should run extremely rough and the sensor voltage should increase to greater than 3.0 volts.
6. If the sensor voltage does not react but the engine RPM does, replace the DPFE sensor.

 

[97ranger4x4]

How do I check the voltage of the wire with one of these?

Do I just take the + pin lead and put it through the wire coating?

And the - one goes where, just to a ground?

also where should the dial be selected? Sorry I never use this thing and never really understood the whole volts, amps and all that technical mumbo jumbo.

 

[bikerboy]

Yep you just probe through the wire insulation. And the (+) one goes to the wire and the (-) one goes to ground when you are checking for power on the wire. If you are checking for ground you want to put the (-) one into the wire and the (+) one onto the battery positive. You want the Digital Volt and Ohms Meter(DVOM) set to DC 20 I'm pretty sure. Don't be shy to ask questions that what we are here for. We'll help with anything we can.