I'm in the same boat as what you're thinking - it seems almost impossible. my one hold-out was hearing from the ECU repair company that they see this happen on occasion - but if you're saying its very rare then I'm even more skeptical....

Okay, so I left everything I'd unplugged before unplugged at the time of todays tests..
Oil pressure, Crank, Cam, IAT, Coolant temp, AC Clutch, TPS, IAC, MAP ALL O2's, and VSS... Battery temp, speed control vacuum solenoid...
I didn't have the coils disconnected today, but I did check yesterday with them disconnected - before I had re-disconnected the O2's and didn't find anything different. Fuel pump was removed yesterday and no change.. Actually wouldn't I have eliminated most sources yesterday with the fuse/relay purge?

I suppose that still does leave a couple of sensors I haven't actually disconnected yet...
Park/Neutral sensor - figured it was acting normal so never tried since it seems a little awkward to get removed.
Transmission temp sensor - need to find that one...
Variable force solenoid - no idea where this is or what it is... Actually I'd say most of the C2 connector I'm not sure what or where I'd be disconnecting things...
Generator source - just disconnect the alternator?

Though now that I think about it - I think I've eliminated other connector's sensors by unplugging C2 and C3 and still finding 5V on the MAP return signal wire yesterday....Only thing left in C1 is the Park/neutral safety switch... Guess I'll pull that tomorrow and see.

Man... It's really tempting, honestly. I'll tell you it'd be a lot nicer working here than that other situation! Sadly that, or even buying another PCM, might turn this "awesome deal" into not a deal at all if I spend much more money on this project... $2k for this truck and a working plow plus a parts plow. But we're looking at about $3k now in expenses. Some of which are things that were actual fixes though. Still have maybe $200 or so to go but that's just improvement fixes/upgrades.
I think I'll send mine in to that company and see if they can repair it - and if not I'll be getting my $400 back. In the mean time I debate if I should try to find another PCM or not...
This is starting to really get to me. I gave up after my post earlier today and went and worked on other projects I was planning to have done by now thinking this was going to be an easy home run. Haha! Actually got quite a bit done when I wasn't banging my head against this issue....

 

I don't think the park/neutral switch on the trans is even involved with the PCM. That aside, I think that one is on the 12 volt side. As are the coils/injectors. The A/C pressure switches, I am not sure, but, I *think* they are also on the 12 volt circuit, along with the compressor. Trans temp, "variable force solenoid" are both IN the transmission. The sensor is 5 volt, the solenoid is 12. 8 pin connector on the trans, drivers side, 'bout halfway back for those. Major pain to get to, especially if you have 4wd.

Yours is the ONLY truck I have seen with this issue. Of course, my only experience is here on the forums. I am sure the repair company probably sees thousands of PCM's a year..... so, they may be right there. I just don't know.

Well, once it is running good... yeah, you'll have a significant investment there, but, could you buy one that runs as good for the same money? I doubt it. I just spent 2500 bucks on a truck I only paid 3300 for.... to get the front end rebuilt. (I didn't wanna do it.....) But, it still runs good, starts every time I turn the key, gets me where I need to go, (and some places I really shouldn't go.....) I couldn't replace it for what I spent, thats for sure.

 

So the only thing left is the trans temp/variable force connector. I believe I've seen it then - just "up" from the park/neutral safety when laying on your back under the transmission?

I do have 4wd - and yeah it's pretty awful getting up in there.

I'll have to pull that one tomorrow and check again.
I'm still curious - outside of this one connector - the VSS is the only potentially shorted wire scenario I've come across in the whole truck. Could the VSS have wiped both PCMs since I didn't find it until yesterday?

Also would really suck if it was sensor/solenoid internal to the trans causing the issue since it was recently rebuilt....

I suppose you're right - though the more I watch the market I am approaching what people are asking for running/driving ones in similar condition...
​​​​Worst case and some point I'll have to fly you down or take this thing to a shop. Hahaha
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I don't think a failed sensor could smoke the PCM. Worst case, it sees 5 volts on the sensor return, which it should know is wrong, and set a code. That, and if the VSS failed in any fashion, your speedo wouldn't work.

There is another sensor on the side of the trans though, output speed sensor. Also on the drivers side, above the 8 pin connector.... maybe a bit more to the rear.

 

Do you know what could smoke the PCM then??
I'd read that a bad alternator could produce AC voltage somehow and smoke the PCM? Though this thing has a brand new alternator... well, supposedly the guy put it in a few weeks before he listed it for sale. Looks new.
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just curious because if this doesn't pin something down tomorrow if there's something else I could look for...

I'll disconnect every sensor I can find. At minimum those two on the transmission.

could the injectors be messing with this? Other than the tranny sensor I think all that's left is passenger injectors to disconnect and test - I disconnected the driver's side in testing yesterday..

Is it possible to take off the intake with the engine in the truck?Unless their barely threaded in - seems like there's barely or maybe just enough room with a box end to get the last intake bolt under the firewall loose...?

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Alternator naturally produces a/c current. There is a rectifier bridge in there that changes it to d/c. If that fails..... the entire electrical systems starts acting weird. Shouldn't kill the PCM though. More likely its just an 'age' problem. These PCM's are know for weak solder joints, etc...... That usually results in an open circuit though.... not a short.... Would be interesting to open up the PCM, and see if anything obvious presents itself.... but, odds that you can actually SEE the problem, are pretty thin.

Do you see 5 volts on the signal return wire for all the sensor? Just some of them? Or just the MAP?

 

Had a couple jobs to do in the morning - one of which required me to run through town and on my way through I saw that somehow the parts store was open ...? Haha!

Stopped in there and got a PCM ordered - sort of. $219 with 1yr warranty! Programmed and all. Even though it showed "in stock" the parts manager guy was being all weird and said he was going to put in a request and they'd call me Monday about coming back in to pay and get it ordered .. Gotta go to town on Tuesday anyway so I suppose I'll do it then.

Definitely going to ask for a refund from the place I ordered the other that I still haven't gotten...

Anyway - got to the truck and pulled everything I could get my hands on...

​​​​​​VSS, EVERYTHING attached to the transmission, ALL O2s, ABS, Coils, AC clutch, AC-something (was attached to firewall with the AC lines running to it), Crank, Cam, IAT, IAC, coolant temp, MAP, TPS...

Still getting 5v on signal return wires with both PCMs.

Through most of the testing I've been solely checking the MAP wires. Though I have been intermittently checking crank, cam and TPS as well - out of convenience - found a spot to stand where I can reach them all from the same position.. I checked all 4 today (at the PCM for the MAP and at the connectors for the others) with both PCMs and have 5v on signal return at all of them.

Next step is to start looking up the cost of flights from MI to IA... 😂😂😂

 

If you can put me up, (put up with me?) for a few days, that's doable.

That is just the weirdest thing. The signal return wires have NOTHING in common.... That should not be happening.... and with TWO PCM's????? That is indeed a real head scratcher....

 

Are you a former Dodge tech? Or just only had V10's your whole life an have dealt with every issue under the sun? haha

Definitely going to wait for this third PCM before I call it quits for what I can figure out. I'm honestly at a loss on what else I can do here. I think we've tried about everything we can try here - unless you're keeping some secrets....
Then there's this sinking paranoia in the back of my head that when I plug in a sensor it'll grenade the brand new PCM all over again HAHA

 

I was an auto tech for a LOTTA years. Worked on all sorts o' stuff. Learned a LOT working at a GM dealer, even though I was a Service Writer, not a tech. I was busy in the morning, and toward closing time. Rest of the time, I was fairly bored, so the service manager had me help out the techs with their sticky problems. Learned a lot about fuel injection, ABS brakes, and such. Worked as a wrench turner before, and after that, on and off. Basically, I been workin' on 'em for more than 40 years. Ran my own shop for a while too.... but, when the economy tanked in the early 2000's, so did my shop. Today, I am retired, have been for a while now. (health issues) I am more likely to pay someone else to do my wrench turnin' for me..... I just don't have the strength or stamina any more. Electrical though, that's brain power. (hopefully.....) Mine still works reasonably well. Most of the time......

If you have the same problem with a third PCM....... I think my brain will explode.