What is the difference in the ECU for a manual trans and an auto trans. I have a 95 dakota with the 3.9 engine/auto trans and the computer went bad. I got one at the salvage yard but it was in a manual trans truck. I didnt know they had two different part #s. Anyhow, I put the computer in and the truck runs fine but the button to turn on/off the overdrive doesnt work. I dont know if it worked before because I inherited the truck when my grandfather died so I cant ask him. Any help would be greatly appreciated.

Thanks,
Danny

 

I don't know the differance in the PCM's, but there is one, because they have one for a manual and automatic. I would think the main differance is: ability to illuminate the "upshift" light (located, I believe, by the "1" on the tach) for the manual, and the ability to shift into OD (4th gear) on the automatic.

 

I would have to agree there. I wouldn't imagine mother mopar creating two different pcm's without a reason. Although there have been other things in the past..........