Hi all. I am new to posting but have used the information many times. My 1992 3.9 AT Dakota quit starting. I tracked it down to the PCM. I went to the junk yard and was only able to find a PCM in a 1995 3.9 AT. I bought that and put it in and the truck starts. However now it shifts poorly and almost dies at time. It appears to go away when the truck is warm. I also ordered the correct PCM online. at a much high price. The question I have is should the 1995 PCM work, and I have another issue. Or do I need the PCM for the 1992. I would like to return the one I bought on line if the 1995 should work.

 

I know they changed the internal passages in the 95 auto transmission. IDK if they changed how the PCM interacted with it.
here is a link to RA for a comparison. Looks like they have two for auto trans. One federal emissions one CA emissions.https://www.rockauto.com/en/catalog/...computer),2896

 

Thanks for the response. As I have search the internet I have found differing comments on the compatibility of the PCM's. One thing I did see is that the PCM wiring connections a a little different on the PCM plug to the transmission. Since i do not know what the wiring is doing I do not know if it is a naming issue or an actual issue.

 

Between 1992 and 1995, there were several changes made - the pressure regulator was moved to the tank and set to a higher set point, and the injectors are larger.

This causes swapping between 92/93 and 94/95 sometimes problematic.

Yes, you should have a 1992 (or at worst, a 1993) PCM; the 1995 is making assumptions that aren't valid about your truck.

One more thing - somewhere in there, the design changed from a feed through VSS to a dead end VSS, and the speedometer changed from a mechanical drive (to 1993) to an electronic (1994 model year and up) design. Somewhere in there they also changed from the VSS being the primary signa for speed to it being a combo of the VSS and the anti-lock rear axle sensor.

Also, the transmission end is the same for both.

Just for grins, I've attached the PCM sheets for a 3.9/5.2 for both years as PDFs.

RwP

 

Thanks for the information. Looks like I have to install the exact match PCM I bough online vs my 95 junk yard version. I wanted to make sure I did not open it up if it was another issue with my truck. The $20 I spent on the junk yard PCM was probably cheap diagnostics.

 

I actually have a 92 3.9 auto like you, and I'm running a 95 PCM in it. Not to be a wet blanket, but I'm not having any of the issues you're describing since you put the 95 PCM in. However, on a positive note for you, I am getting crap-tastic gas mileage (11-15 MPG), which kinda makes sense given what Ralph said about the injector size change. So for that reason alone, you may want to consider keeping the correct PCM you ordered. Only reason I'm running a 95 PCM is because the 92 PCM will not allow me to set the fuel sync with the particular scantool I have, whereas the 95 PCM will.

 

Do you know what part number you are running? I have the 5602 8483 from the 1995. The broken 1992 PCM was 5602 8741

 

What you can do is, after it's set, swap the PCM back and see if the gas mileage improves.

I'd also toss in a new O2 sensor, since I bet the old one is bad from being overfueled.

RwP

 

The sticker is long gone on the 92 PCM. The 95 PCM is a 5602 8339.

And yeah Ralph, I checked the fuel sync again right after I posted, and went out and swapped the 92 PCM back in LOL.

 

Shaderabbit, thanks for you part number. I will have to find out what you get from each different PCM number.