1995 Ranger XL 4x4, 3.0L, 145K

For a while now my truck has been giving me the P0401 error. Before i knew about this forum i replaced the EGR valve with a new one from the dealership. Of course, i wasted $75 on the part. I then found this forum and decided to replace the DPFE (autozone calls it EGR valve pressure sensor), and the two vacuum hoses that connect to it. Still get the error. I then changed the EGR vacuum solenoid, only $20, then cleaned the MAF sensor, poked a wire through every hole i saw looking for carbon plugging, and unplugged the battery for 30 minutes. I had a hell of a time starting the truck, but it started after a few minutes. I drove about 20 miles and the stupid P0401 error came back. I don't know what i'm missing, i think i have replaced everything.

I'm not sure if this matters, but i will throw it out there anyways. I am using a mechanical thermostat because the original one stopped working. Also, if i fill the gas tank up completely(which i don't anymore), it will leak out a little bit. I think there is a hole near the top of the tube that goes from the tank to the gas cap. Not sure if those two things effect the P0401.

Anyone got any advice?

 

id suggest following this guys post. its about a diff model vehicle but he does an EXCELLENT job of the troubleshooting

https://www.ford-trucks.com/forums/6...ighlight=P0401

Matt

 

also, you dont use bosch plugs do you?

Matt

 

Ya, i think i am using Bosch plugs, what's wrong with them?

 

ok, ive got another post to make..... here is a thread on this very problem in a ranger

https://www.ford-trucks.com/forums/5...ighlight=P0401

and this one with someone who got it fixed!
https://www.ford-trucks.com/forums/5...ighlight=P0401



Testing the EVR "Its on the back side of the coil pack(where the plug wires plug onto). "

 

On the hard restart, did you pull the ECM power fuse, or remove the battery B-/gound cable, for a while, to reset the computer, after cleaning the MAF sensor & doing all the EGR system relacement of parts?????

If you have a leak in the gas fill piping, it'll suck in extra unmetered air, when the gas fume recovery system is trying to purge the gas tank of fumes, on start up & upset the air to fuel ratio, so maybe this is having some effect on the hard restarts, as it could cause the A/F ratio to go lean.

I'm not sure if the system has some vacuum applied all the time, or intermittently while driving, or not, but if it does, it'll act as an unmetered air/vacuum leak & upset things.

There is an orifice under the EGR valve that the DPFE uses in it's feedsback role. to
sense the difference in intake & exhaust manafold pressure, that if plugged, will corrupt the signal the DPFE sensor sends to the computer & the computer will then get confused about what to tell the EVR to do, in controlling the EGR valves work duty cycle.
You must remove the EGR valve to see/inspect/clean, this orifice. If the EGR alve you relaced was carboned up, it might be worth removing the new EGR valve & inspecting/cleaning this feedback orifice.

So, as fordboy has suggested, you need to do some more EGR system trouble shooting & imo also look to the leak in the gas fill piping.

Let us know how it goes.

 

i would suggest replacing the bosch plugs with some cheap ngk or the stock motorcraft plugs. rangers and bosch plugs do not get along

Matt

 

On that one hard restart, i did unplug the neg battery cable for over half an hour while cleaning the MAF and replacing the EGR solenoid. Other than that one time, i never usually have a problem with the truck starting. It's starting fine now so i'm not worried about that. As for the gas leak, i guess i'll go and filler up all the way tonight, lose a $1 worth of gas to the concrete, and look for the hole.

It turns out when i changed the plugs about 6 months ago i used Autolite Platinums, not the Bosch ones. Any problem with these?

I did some of the checks last night off of the first link given to me.
Power to the EGR regulator(solenoid) was 11.6 v with key on
Pin to Pin accross EGR regulator(solenoid) was 34 ohms with key off
Power to DPFE was about 5 v with key on (it was 4.? v, in range though)

He had some checks to do with the engine running, but i'm really not an electrical expert so i'll give those another try tonight. I have a digital multimeter and a vacuum pump, but yesterday was the first time i used the multimeter, and i've only used the pump for bleeding the brakes. I'll figure it out sooner or later though.

One last thing, when i was cleaning everything and looking for clogged holes, i sprayed brake cleaner down the metal tube(manifold tube??) that goes from the EGR valve to the exhaust header. I could see the brake cleaner dripping out the bottom where the tube connects to the exhaust header a little bit. Should there be a gasket where these meet? Or does this connection get better once the exhaust header heats up and the metals expand.

Thanks for the help so far...

 

Sounds like you found your problem... it's possible that tube is cracked down at the manifold.

I'm surprised you're not noticing an exhaust leak there. And no, it shouldn't leak at all...

 

I removed the manifold tube and didn't find any cracks. I cleaned it up and made sure to tighten it on there good, it may have been a little loose before. Anyways, it doesn't leak anymore. I cleared the codes, drove 40 miles, and I'm still getting the P0401 code.

I've been reading a lot of these forums on this code. From what it sounds like, the EGR doesn't start working untill after the truck has warmed up. I said in my original post that my temperature gauge wasn't working so i installed a mechanical one. To do this i removed the temperature sender and installed the lead for the mechanical temperature gauge in its place. So i'm not sure if the truck is recognizing if it is at operating temperature, and adjusting the EGR accordingly.

Does the EGR system look at the temperature sender when determining if the truck is at operating temperature? Or is there some other sensor it looks at?

 

The temp gauge sending unit isn't used by the computer. The computer has it's own separate engine temp sending unit.

 

When you put the mechanical guage in did you make sure you had the temperature sending unit or did you get the ect sensor connection that can use some codes if it isn't hooked up.

 

Sorry, i'm kinda confused about the last question.

I installed a generic autozone special mechanical temperature gauge, the end of the metal line for the gauge installs in place of this part:

http://www.autozone.com/R,APP263798/...ductDetail.htm

So the wire for the part listed above (temperature switch??) is just hanging out not connected to anything. The mechanical gauge does not connect to any sensors or to the trucks wiring in any way.

 

The gauge temp sensor has two wires going to it's connector, the computers engine coolant temp sensor has three wires going to it's connector, so how many wires are going to the connector thats hanging loose?????

 

Actually the one that's hanging loose has only 1 wire, i'm pretty sure its called the temperature sender. The sensor next to it with 2 wires is still plugged in. I didn't see one with 3 wires.

I decided to stop confusing myself and looked in my Haynes manual. It says the temperature sender/("switch" according to Autozone) has one wire and it controls the gauge. This is where the mechanical gauge is plugged into. The coolant temperature sensor(ect) has two or three wires according to the manual.

I guess this means the mechanical gauge is not the problem. Tomorrow i'm going to test the ECT, and replace all the vacuum lines.