Hardcore tech help plz

[twistedtech]

I've got a 99 soreass at work that is just killing me.99 3.o,12v,plain janer nothing special here.So here's the deal.PO1401,dpfe high.Here's the run down.MT2500 show's volts at 5.02,spec calls at idle 1.30 or something like that.Had the pcm tested by bluestreak,pass,voltage varies.DPFE sensor passes( tried old(vantage)tried new,tried working one from twin car)ran new wires.Swapped out all pieces from twin car,checked with scanner all working fine on doner car,not working on customers.So heres the deal,pin 65 instantly dumps out 5.02 koeo or koer no diff ever.Short story,new dpfe,new wiring,new pcm.All checks out well.65 will not offer anything other than 5 volts.I am missing something or this is damn ass good.Got some thoughts?

[shorod]

Do you have the service manual, and if so, have you gone through the diagnostic procedure for a P1401 code? If you don't have the manual, feel free to send me a private message with an e-mail address for you that can accept PDF attachments. I'll e-mail the procedure to you.

-Rod

[twistedtech]

Originally Posted by shorod

Do you have the service manual, and if so, have you gone through the diagnostic procedure for a P1401 code? If you don't have the manual, feel free to send me a private message with an e-mail address for you that can accept PDF attachments. I'll e-mail the procedure to you.

-Rod

Yes I have a manual.Thanx for the offer.I would like to mention 1 more thing.I have been a tech for 23 years,and a drivability tech for about 17 of those years. I am really overlooking something here or this one is a real good one.Once again,thank you for the offer.

[fdunford]

The DPFE should put out 1 V at idle, not 5 V. I'd try to see if you can change the value of 5 by first removing the hoses to the DPFE and take a reading. Then I'd remove the connector it that failed.

Keep in mind there is a 2 trip counter in which the monitor must complete before it will set the code. So a simple swap and no code may not be goving you an accurate picture as to the health of the DPFE.

[shorod]

The troubleshooting guide in the factory service manual goes through step-by-step how to narrow down the problem causing a code P1401. "If this, then check here. Else, measure this" type of logic. Following the troubleshooting guide will help you determine if you're missing something or if you found "a really good one."

The offer still stands.... It sounds like you certainly have the qualifications to perform the various checks outlined in the troubleshooting guide.


-Rod

[twistedtech]

Trust me,I have flow charted my brains out. We are not talking about it tripping the code,be went past that a looooong time ago. I crap you not. So here's my logic. I had twin cars,took ( 1 piece at a time ) the pcm and swapped it out,(key on not even running ) showing 5v,doner car,1.3.Rules out ecm. Swapped out with doner DPFE and new ( ford new), still 5v.Doner car works mint, 1.3. Did ohm test on wiring,passed. Rewired dpfe with new wires,seperate,no good.5 volts. I even cut the wire ( pin 65 ) still 5.02 comming from pcm. There might be an accident with this car soon.

[shorod]

Do you have 5V on pin 65 of the PCM even with the DPFE sensor out of circuit? If so, this probably just indicates there is a pull-up resistor internal to the PCM that is pulling this line high. According to the schematic, pin 65 is an input to the PCM for the DPFE.

When you had the wire for pin 65 (brown/light green) cut, did you measure the voltage from the DPFE in addition to the 5.02 V at PCM pin 65? If not, how big of a problem would it be for you to open that wire again and measure the output from the DPFE?

At the DPFE brown/white wire and PCM pin 90 you should have reference voltage (+5V). DPFE gray/red wire and PCM pin 91 is signal return. If you use pin 91 as your "ground" and measure at pin 90 and pin 65 of the PCM, what voltages do you read? Also, with pin 91 as "ground" what voltage do you see on the brown/light green wire of the DPFE with that wire open circuit?

-Rod

[twistedtech]

When you had the wire for pin 65 (brown/light green) cut, did you measure the voltage from the DPFE in addition to the 5.02 V at PCM pin 65? If not, how big of a problem would it be for you to open that wire again and measure the output from the DPFE?
With just the 65 cut it still gives a 5vt reading comming from the pcm.Nothing from dpfe.( I'm not solid on that but I don't think it read anything,for some reason I wanna say just a few millie vlts.
At the DPFE brown/white wire and PCM pin 90 you should have reference voltage (+5V). DPFE gray/red wire and PCM pin 91 is signal return. If you use pin 91 as your "ground" and measure at pin 90 and pin 65 of the PCM, what voltages do you read?
Yes I have ref 5,as for the rest I think what I will do is call the cust to bring it back and I will document it all.I tested and tested.I can recall retracing my steps 3 times.The prob I am having now is that I can't recall everything.The part that gets me is that I cut all three ran new wires to the pcm,swapped out the pcm I knew worked, tossed on the new from ford dpfe and still had 5 on the pin 65.Then tossed on the knowen working dpfe and still the same.Toss everything back on the donner car and all works right.How in the hell with a rewired dpfe and knowen working pieces is this possible.I will call the customer tommorrow and get it back, I just half ass put it back together so he could have it back for a few days.I will doc every step and post it.I must just simply be missing something here.

[shorod]

Well, I want to be clear that it will help to know what voltage you see using Pin 91 as the meter ground. Pin 91 is what the PCM will be using for DPFE ground. If you are using a chassis ground to make your voltage measurements and your PCM is floating for some reason, you may measure 5V but that won't be what the PCM is seeing. Verifying all the grounds and returns to the PCM might be a logical step.

When you get the car back and post your "report" we'll compare notes again.

-Rod

[twistedtech]

That's where my heads at, i called and it looks like I wont see the car till next week. I've gotta get this thing figured out. In 23 years I have never had a car beat me and I will die before I let it happen now.

[twistedtech]

Well, finally got the car back in and re-ran the testing.Using the Vantage and using ONLY the pcm wiring here is what I found=
Running Test:
BRN/GREEN 5.02 vlt
BLK/GRN 5.02 vlt

Running with DPFE disconnected :
Same as above

KOEO:
Same as above.

A whole new ugly has shown up. I have not made up my mind if it is the same issue or a whole new one, I had 15 codes today. All in that rear harness,rear o2's.IAT,Trans Range,ECT and so on. I think this is an inter issue as it was all well today except the rear o2's.I had to pound the snot out of it to get to go rich enough for them to come off a zero reading then as they cooled off they dropped out again.I am really starting to think that I have a harness issue here. The DPFE is in that harness section but along with the injectors which seem fine. Shorod.........good luck with this.

[shorod]

Wow, 15 codes!!! That was good troubleshooting to realize they are all in the same harness/area.

This car didn't happen to come from an area that has had recent flooding, did it?

-Rod

[shorod]

I forgot to ask, were these measurements of 5.02V made using the PCM signal ground/return as reference or a known good chassis ground? If chassis, it would be interesting to see if there is a difference using signal return as ground for the meter.

-Rod

[twistedtech]

Originally Posted by shorod

I forgot to ask, were these measurements of 5.02V made using the PCM signal ground/return as reference or a known good chassis ground? If chassis, it would be interesting to see if there is a difference using signal return as ground for the meter.

-Rod

Not the chasis ground.You asked me to do the 91 pin and that's what i did. I knew it would be the same but for the benifit of the doubt I did it. So tell me this one don't make you scratch yur head! Not a flodded car, it is an Ontario,Can car but low miles. If you take in to account that if not all but most of those codes from the same harness it make you belive that the harness is bad or 1 sensor is rerading way off and not showing up. Way back at the begining, and in fact, the title of this thread was HARDCORE help. I was not kidding. I am not putting a feather in my cap or patting my own back here but I am the driveabilty tech to go to in our area. For some dumbazz reason I have gotten that label.I hate labels. I know how to do things but I don't know how to tackle this one. I would hate to toss a harness in this thing just on a whim. Someone someplace must have seen this before.

[shorod]

I realize you ran new wires, but with the readings you posted, the DPFE would appear to be open circuit from the standpoint of the PCM.

You are seeing the same voltage on line 65 (brown/lt green) to 1/100 volt with or without the DPFE plugged in. If the DPFE is actually in circuit and doing ANYTHING, that voltage should at least change a little bit. Heck, even if the PCM is able to source a HUGE amount of current from the 5V regulator, I would expect to see some difference in voltage (Ohm's Law).

The next measurement that I think would be beneficial would be to measure the voltage potential between pin 91 of the PCM and the negative post of the battery, then between ground of the DPFE connector and battery negative. With all the codes related to that harness, it seems the most likely candidate that could affect them all would be a faulty ground.

-Rod