Alright - I finally got a few minutes to work on diagnosing the issue.

I'm pretty sure the wires are good between the pigtail and the injectors.

I cleaned up the pigtail with a wirebrush to make sure that the pins were clean - no rust or corrosion was there in my observations.

I ran my multimeter from the white wire pin (59) to the number 6 and 7 cylinder injectors, then ran the same test from the tan wire pin (58) to the injector for number 5 cylinder. All tests showed "0"

I then ran a 12v test light from the battery positive terminal to the pigtail pin 58 (1/4/5/8) and it flickered fine with the engine running. Same test on pin 59 (2/3/6/7) and nothing on the test light.

It would seem that there is no ground signal being sent from the computer.

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So a recap here:

1. Bought the truck with this issue present.
2. Installed a remanufactured PCM from Oreilly Auto Parts - no fix
3. Installed a remanufactured PCM from Autozone - truck ran great for 400-500 miles
4. Installed a second remanufactured PCM from Autozone - no fix
5. Pulled a matching/correct PCM from a wrecking yard - no fix

I can only assume that if I purchased another known good PCM from a yard or a shop, that this truck *may* run right again.

But the bigger question now is what caused this issue? What continues to cause this issue? What would kill the 2/3/6/7 cylinders repeatedly from the computer?

When I pulled the good PCM (the 500-miler), it was a little wet inside the pocket that the PCM sits in inside the cab firewall. We had a ton of rain the last time the truck was driven and was running good. No doubt some water may have gotten in near the computer. But this issue first happened in the summer or early fall and likely not when it was raining (before I bought the truck). The gasket was in fine shape that seals the pocket and the computer from weather, so I am guessing this leak is coming from the windshield area or something else. There are some surface rust areas inside the cab right around the area the PCM sits when installed.

I find it doubtful that water on the otherwise pretty well-sealed PCM would continue causing the exact same issue, but I really don't know.

What could I try next? What do you guys think?

Thanks again so very much for your help!

 

Any suggestions?

 

Inside of the round pins looked green to me. Did you clean the inside or just the out side of the pins?
Also check for the pin being pushed back when you plug the PCM in.

 

Christian, you've got @subford and @rla2005 in here and along with @Conanski they are simply the most knowledgeable.

The only thing I can add is to follow this troubleshooting tree:

https://easyautodiagnostics.com/ford...module-tests-1

And yes, Ford Racing 9mm wires with Ford wire looms are always good. See SummitRacing.com I had a miss and I think it was subford who told me I likely had cross fire between the wires, and I didn't believe it and I couldn't see the arc in the dark with the hood up and the engine running. But dang when I changed out the spark plug wires, there it was! A little clean part of the insulation on both wires where the two wires were touching.

 

The PCM plugs pin #59 is either spread or it is pushed back when it is plugged into the PCM.
Just use a BOB with the BOB extension cable and check pin #59.
If it dose not have a miss with the BOB then you know it is the PCM plug #59 that is bad.

Or you could use a EEC-IV recorder and record pin #59 as you drive.
Else it will show a bad PCM.

Any shop that works on the EEC-IV systems should have a BOB and EEC-IV recorder.

 

Thanks @subford, I'll give it a try.

What's a BOB?

 

Brake Out Box:

Attachment 282975

/

 

I replaced the ECM (i.e., PCM) in my wife's Dakota four times thinking it was the component. It was a dirty 32-pin connector. ("Mechanics look to the component, electricians look at the wiring.")

Application of these products cured my wife's Dakota "PCM" problem:

Micro Q Tips:


CRC Contact Cleaner (use liberally, it's cheap):


Deoxit D5 Contact Cleaner (use sparingly, it's expensive):


Finish with, and this is considered voodoo by some,

Deoxit Gold Contact Conditioner (use sparingly, it's expensive):


My personal experience is never to put dielectric grease on a low voltage signal contact like a PCM. Dielectric grease KILLS electrical signals! Ducati motorcycles used to advocate it on their dirt bikes, and then issued a revision TSB advising against it.

Deoxit Gold, is a similar grease to dielectric grease, but supposedly the gold flakes make contact that the grease would inhibit. (That is why some call it voodoo, others in the computer industry (e.g., low voltage signals) swear by it.

Try it. Clean both pins and receptacles.

@Tedster9

P.S. There are also micro round files out there for cleaning receptacles. I advise against them. Removing contact material mechanically is to be avoided if at all possible.

 

What should my voltage be when I'm testing pins 58 and 59? Does anyone have access to the values I should see on the PCM pigtail? Thanks!!

Nevermind, I had forgotten that it's sending a ground signal! I'm hoping to get this sorted out this weekend.

 

Ok, I made myself a makeshift BOB and exclusively tested Pin 59.

A while ago, when I was at a wrecking yard, I cut off the PCM pigtail (female/harness end) from a donor truck. Today, I pulled a good pin out of that pigtail, and then gently removed pin 59 from my truck's pigtail, and put the donor pin and wire in its place.

I then connected the pigtail back to my PCM, fired it up and used a test light on both pin 58 (the four cylinders that are firing properly) and pin 59 (the four that are not firing at all).

The test light on pin 58 flickered appropriately, showing ground signal being sent out of the PCM. The test light showed no activity at all on pin 59. It's dead. I did clean the donor pin and wire and gently compressed the pin for a nice firm fit before installing it in the pigtail. I'm getting good conductivity from the round pin connector to the end of the cut wire too. There's just no signal going out of the PCM as far as I can tell on pin 59 (cylinders 2/3/6/7).

So I'm just a bit stumped. I've had four PCMs in there since this issue started up again. Two were remanufactured units from Autozone and O'reilly Auto Parts (one each), and two were junkyard finds with matching numbers to my truck. On one of those junkyard units, I even soldered in three new capacitors to be on the safe side (tested it before and after), but did not correct the issue either way.

---

My thoughts/questions:

• I've read horror stories about getting faulty 'remanufactured' PCMs - one guy on one of these forums had to try NINE remanufactured units before the last one worked. So… is it just a matter of fact at this point that I have a bad PCM still?
• Does the ICM (injection control module) have anything at all to do with this?
• Where else should I look at this stage?
• Should I just go and keep buying remanufactured PCMs until I find one that works?
• I'm pretty sure my windshield leaked after driving through a very heavy rainstorm (months ago). That was the only condition that occurred where I went from a good running truck to dead inner cylinders again. If I have a leaking windshield, what's the best way to seal that baby back so that when I do get this beast running good again, I won't find myself in the same old situation again?

Thanks so much to all of those who've taken time out of their lives to help with my problems with this truck. I appreciate each reply, and have learned a ton along the way. I feel like I'm just about to cross the finish line and with a little more help from you all, I'll have a good thread of info for the next guy who struggles with this issue.

����

 

I have heard of this before and it was the PSOM sending a 90+ MPH signal to the PCM.
So the PCM cuts off a bank of injectors until the speed is down to some set MPH in the PCM.

I do not remember who posted this years ago but think it might have been Mark Kovalsky, the transmission engineer for Ford.

 

@subford - SUPER enlightening. I'll start testing that area next. I found this video: which addresses PSOM repair for a 1995 Ford F-250, and he's providing some great ideas for me to check into.

The rabbit hole continues to go down, down, down.

Stay tuned…

 

You could just unplug the PSOM at the cluster or pull out the VSS pin at the PCM and see if the bank started working again.

 

Ok, I pulled out pin 6, left the battery disconnected for 20 minutes, then fired it up. Still misfiring, no change there.

Would pulling the VSS (pin 6) be a conclusive test on ruling out the PSOM as a cause?

It's interesting because I do have the CEL on (has been since day 1), and I do have hard shifting (automatic 40D transmission) from first to second. Not sure about higher gears, because I'm not driving it due to this problem. My water temp gauge also doesn't work. My mechanic said it was the engine temp sensor near the distributor, so I replaced that but the gauge still doesn't work.

 

I was thinking more like pin #3 for the VSS.
Pin #6 is a ground.

If the CEL is on it means you have stored codes.
What are they?