Contuniues Check Engine Light need help to fix.....

[SRD]

Hello. I have tried to repair my 99 ranger XLT 3.0 for over a year with no luck what so ever. I have court soon as I cannot register the truck got a ticket as I cannot get the CE light to go off to pass SMOG so am at risk of losing my work truck all together.

The truck CE light just will not go away no matter what I do to fix it. I am not a mechanic just trying to fix my own truck if possible.

**ISSUE: I have had multiple CE lights that mix as I chage the DPFE. I have cleaned and replaced my EGR, etc......I am jst lost.

The CODES finally went away on their own after I replaced the DPFE and Pigtail...but the code still showed in the OBD2 so I cleared it and went to get a SMOG. The smog guy said it failed as I cannot clear codes I have to wait 50 miles...so I did and the light came back!!!!!!!!!!!!!!!!

**WHY did it go away on its own then come back with more and more codes over and over?????

CODES are as follows: They codes mix as I change the DPFE sensors but never go away.....I have used OEM and 3rd party. OEM pigtail....I changed gas cap.

p1400: DPF EGR Sensor Circuit Low Voltage Detected

p1401: DPF EGR Sensor Circuit High Voltage Detected

p0402: EGR flow excessive detected.

*Any idea of someone who can walk me through wat to do step by step to help me discover the actual issue would be MUCH appreciated.

Thanks

SRD

 

[pentode]

I need to check the manual to make sure but I think a bad ground could cause at least 2 of those codes and bad wiring could definitely cause all 3. Have you checked your powers and grounds to the sensor?

You should also be able to backprobe the signal wire from that sensor, key on engine off and get a voltage reading and see if it's sane. Again I have to double check but I'm thinking maybe about half a volt not running?

I believe the supply voltage to that sensor should be 5V

 

[SRD]

Hello. Thank you for responding to my post.

I do have a tester but am not familiar with automotive testing just figuring it all out. I looked for videos on how to test the DPFE sensor but not one I could fully understand. I did replace the Pigtail wire and matched it with OEM factory Pigtail with a Motorcraft -wire assy (p) (WPT1044) Black pigtail wire.....I matched up each wire from plug. 1999 XLT ranger flex 3.0....

If you happen to have a video that can show me how to test that part I would appreciate it...I never heard "Backprobe" before as I am not very advanced electrically but did watch this video below I think showed me what you meant? I need "t-clips" and alligator clips to test the voltage.....I will seek to get the stuff I need.

Backprobe video:

So far seems I to need to test for a Bad Ground?...Test the DPFE sensor "Voltage" and send back results?

Thanks for helping me figure this out....

SRD

 

[pentode]

No problem at all, I'll do what I can to help but there will be others on here with more experience with your exact hardware.
Backprobing just means probing from the back side of the connector. This lets you check voltages etc with the connector still plugged in. Some of these connectors are weathertight though and might be difficult or impossible to backprobe so you might have to get a bit creative. This is why some people use piercing probes instead. You can use t-pins or any other pin really that allows you to reach the metal contact inside the connector- you just want to do as little damage as possible for obvious reasons. And you need to make sure that whatever pins/probes you use, you don't short anything together as this will just cause more problems and even damage.

I need to find a better diagram than what I have but there are 3 wires going into the DPFE sensor. One will be your 5V (key on engine off), one will be ground, and one will be the actual signal voltage.

First step is to see if you can find a way to probe those voltages without damaging the wiring or the connector. Rather than probe at the sensor itself, you might be able to trace each of those wires to another spot with connectors that are easier to probe.

If you need any pointers about how to use the meter, feel free to ask.

There's another post on here where someone posted a really good reference for understanding the procedure of what you're trying to do, although it's for a different Ford engine.

Help with DPFE troubleshooting

I am working on a 2000 Ranger 3.0 5 speed and trying to diagnose a codeP1401 for "DPFE high voltage" and I am getting 4.98 volts at both wires even with the key on and the DPFE unplugged. Is this normal? I've tried searching but could not find what it should be reading at the plug with the DPFE...

www.therangerstation.com

Last thoughts for now, at some point, check the integrity of the hoses going into that sensor too just to make sure. My gut tells me that since you have both high and low codes that it's going to be a wiring problem but that's just a gut feeling. Good luck!

EDIT: you said the codes change when you change sensors- what codes do you get with the oem sensor installed?

 

[Mechrick]

The p1400 means the DPFE sensor voltage went below .2 volts (which it should never do if plugged in).

The P1401 means the DPFE sensor voltage went above 4.5 volts (which it should never do if plugged in).

The range of in circuit voltage is .2v-4.5v. If the sensor is plugged in and all connections are good the sensor voltage should never go outside of that range.

Inside the PCM sensor circuit there is TTL logic that when disconnected will float the voltage on that pin to source voltage, whatever that happens to be. In the case of a 5v referenced circuit that would be 5v. So with the DPFE sensor unplugged (or a break in either the wire or the ground reference wire) the DPFE voltage going to the PCM will read 5v (or very close). That trips a P1401.

A P1400 will almost have to be a short to ground in the sensor wire or internal in the DPFE sensor itself (or PCM). Very rare.

The P0402 simply means the DPFE sensor voltage is reading greater after the truck is started than key on engine off. This can only be caused by a stuck open EGR valve or perhaps extreme back pressure.

Make sure the DPFE hoses aren't switched.

Double-check the pigtail to make sure it's wired correctly.

 

[SRD]

Hello. Thanks for the input. I matched up the pigtail as image shows. I also went and used a Meter to test the DPFE with "Key On" and took the images attached. I am not a Pro or even sure I did it right but I do not get .5v...

Are these correct? What to do from here? I never traced a bad ground before so not sure of process...thanks for all the support!

SRD

 

[pentode]

You need to find a way to test the voltages on those wires with the plug plugged in. (and key on) If you can't probe into the back of the plug, perhaps you can test where you spliced them together?

To test, connect the black lead to ground, either batter negative or another good clean ground like the engine block or cylinder head, and then touch the red probe to each of those 3 connections. One should read 5 volts, one should read zero, and the other should read something between .5 and 4.5V

 

[Curious Hound]

You can backprobe by sticking sewing pins into the wires. Just push them through the insulation so they touch the wires internally. Then attach your meter to the pins.

 

[Mechrick]

Technically, back probing doesn't pierce the insulation. You slip a conductive needle between the plastic connector shell and the wire so that it touches the blade/pin in the connector.

If you do pierce the wire, when you are done, seal it with a dab of RTV or some nail polish.

 

[19Walt93]

You can backprobe by sticking sewing pins into the wires. Just push them through the insulation so they touch the wires internally. Then attach your meter to the pins.

Please don't do this, you're apt to end up with corrosion in the wires that will cause some weird symptoms and be hard to find.

 

[SRD]

Hello. I was finally able to test the ground wire; just making sure I am doing it right before I continue with the other two wires if needed.

With the KEY ON...I took the BLACK end of the test probe and placed it on the Negative Battery Post. I took the RED probe and placed it onto the DPFE pigtail green GROUND wire where it was spliced to change the pigtail.

The meter was set to DC Voltage. The meter bounced a bit but generally stopped on 5v. Tested several times.

I was told 5v is correct...so I am doing this right? Seems this wire is Ok....

Thanks for the input!!... My power animal is a turtle...so I am a little slow sometimes.

-SRD

 

[SRD]

Sorry, forgot to add a pic of the DC voltage....stops between 5.00 and 5.05 volts.

Thanks.

 

[Mechrick]

I'm showing the color codes as:

Brown/white 5v

brown/lt green sig

gray/red sig return (gnd)

You are getting 5v on the signal wire (incorrect).

Do the same test but move over to the gray/red wire. that one should show ground (or very close).

 

[SRD]

Wow! Thanks, for the fast input! I was at my truck and did the same test on all 3 wires per your instructions with the following results.

1. Brown/White 5.08v
2. Brown/Green 5.05v
3. Grey/Red 31.2v

So, this is not at all what I should be getting I take it?

Also, I had these issues before I changed the pigtail....thought that might have solved it. Guess not....

-SRD

 

[Mechrick]

Is that a typo on the gray/red wire?