Howdy,

After reading many posts here, it seems to me the PCM is a bit of weak point. I've read the location in the engine bay and exposure to too much heat is the culprit--which would seem logical, though alloro, whose posts I've quickly grown to respect, doesn't believe the PCM gets very hot in that location. Is there a definitive failure explanation I missed? Any chance they aren't failing at all, but rather the contacts have oxidized? Anyone crack a failed unit open to look for obvious signs of component failure, like scortch marks or swollen caps, etc.?

Thanks,
Geoff

 

Not a definitive failure explaination as such, all are guesses at this time that I am aware of, unless one of the PCM rebuilders have ever chimed in on what they have found. Now some of the PCM rebuilders have said on their websites to make sure the wiring harness is in good shape for a frayed wire could short out and blow the PCM. Yet some members here have as you pointed out changed the PCM and all was well again. Your theory of the corrision on the plug has also been discussed and one or two have fixed the problem that way. As Alloro has pointed out do the simple things first like check/clean the terminals and check the grounds and other items before declaring the PCM bad. Unless you have a newer digital odometer that says "No Bus", then replace the PCM.

I have not directly been involved with a fail Dodge PCM just yet. I did open a Ford up one time when nothing else seemed to be at fault and found that it had scortched the lid and board. It would not run the fuel pump or injectors but fired the plugs with no problem.

 

FWIW I think I killed my last PCM when I had a heater hose rupture...
hot steam will kill a PCB in no time...

 

When temps got up over 95+ and the van was driven about 20 miles, we stopped in at the Cracker Barrel to eat. Came out and the van would not start. If anyone recalls, I had to do a bunch of funny stuff until the PCM cooled down. Then every worked once again.

The PCM on our vans is in a dumb place. If can get wet from around it and heated in the engine bay.

 

They're basically evolved switch boards, right? What if you replaced the pcm with a bank of individual switches wired in correct series to each other according to the schematics? Most of these automotive switches last much longer than the pcms, and if one does go bad, it'll be cheaper to replace the one switch versus the whole computer, right?
That's where I'm at with solving the mystery of why my truck won't start.
Good luck