I have a 98 ram 5.9 auto 2500. The alternator is not charging, but has been tested and is fine. i was told it might be a bare wire, but cant find any. Now i was told it could be ecm, so will a ecm out of 98 2500 5.9 manual work on my auto? part numbers are different. mine is P56046 347AD. this one in P56040 137AA. Also, if it ecm would that keep tranny from shiftimg automatically. Right now I have to shift manually, and also it will not go into od. Thanks for the help

 

The voltage regulator is in the PCM (great design) You'll need to find and auto PCM , or maybe the dealer can flash the the manual one you have for your truck.

 

Would that also keep the transmission from shifting automatically and into OD? This all happened when I hooked a trailer up to my truck.. Like I said, I have chased wires for hours and didnt find anything

 

Pulling a trailer with OD is a no-no.

You can go to the DIY/FAQ section and download service manual and parts manual. Check the transmission section. Good troubleshooting steps there. Shifting problem is probably not a PCM issue. Far too many people change out PCM only to discover that it is not their problem, and far too many receive PCM's that are defective.

PCM's seldom fail, but stores and dealers appear to push sales.

 

I wasnt pulling it in OD, it was out of od.. I read that the transmission might not be getting enough amps to shift. ive had the battery and alternator tested 3 times at different places and they all say they are both good. In fact, I put a new alternator in and still wouldnt charge. The tranny problem and charging problem happened at the same time.

 

A manual tranny PCM, in an auto! Who know's how it will react. Probably not to well.

 

My guess it would act like you had the transmission unplugged. No automatic functions, no TCC, no O/D.

 

That is how it acts, but its not unplugged. If the pcm is bad, would that keep it from shifting? Like I said, I read somewhere , or heard from someone cant remember, that if its not getting enough amps, the transmission will not shift. I dont know if the trailer I was pulling shorted something out. All lights worked correctly, but when i pulled it is when all this happened, and cant find a bad ground anywhere. The alternator will not charge battery, both have been tested and are fine. I was told its probably pcm, but do not want to buy a new one and it not be the problem. Any other suggestions on what it might be. I found a used pcm, but one is from a 5.2 auto, which I am sure probably wont work, and other is from a 5.9 manual, which I was told wouldnt work. do the p/n off psm need to be exact? Thank youto everyone for input !

 

If you have a PCM from a manual trans truck in there, there is no programming to run the trans, therefore, it won't.

 

For something as elaborate and important as a PCM, I would not dare mess with the wrong part/part #. Asking for trouble....