Are their only 2 variations of the 91.5 ECM? One for manuals and one for autos?
I tried searching parts places and other sources, but no one listed any OEM part numbers. Some "repair" shops inferred that there might be while the auto parts stores only list auto or manual transmissions as any difference.

 

I'm pretty sure there is, when i got my 91.5 PCM off Mark Nixon, he said i needed a manual trans one and that's what he sold me.

 

Yes there are only the two...but you can use an auto one on a manual truck if you ground the neutral safety switch wire. At least that is what I have found by reading through the archives here on the board.

Also a couple people have said they have used a PCM from a 94/95 cummins truck too.

 

I have an ECM in my manual truck that was out of an auto. It works just fine until you bring up the codes. It registers a code saying that my over drive doesn't work.Not a big deal.

 

thats good to know, figured there wasn't that big of a difference.

 

I was wondering if both ECMs had cruise control built in, just not used on models sold without. All the wiring is their, I was hoping all I needed to do is ad the switches and servo.

 

I don't know for sure but I would say that all ECMs have cruise in them.

 

What does the ecm control?

 

Cruise, alternator, overdrive. Pretty sure there are a couple of other things also, but can't think of them at the moment.

 

The alternator is external on 89-91.5. Its biggest function is controlling the grid heaters. Other than that it is cruise and OD, if you have them.

I have all the other parts off a 93, so it won't cost me anything but time to find out if the cruise will work or not.

 

ASD Relay, Air Heaters, Tachometer,Air conditioner (WOT cutout) wait to start light, wif light.