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Auto 3.9L Dakota with a manual ECU

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Auto 3.9L Dakota with a manual ECU

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Old 04-23-2019, 08:23 PM
blackbeemer
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Default Auto 3.9L Dakota with a manual ECU

Hi there guys, recently got a pretty good condition 1995 Dakota Sport with the 3.9 V6, AUTOMATIC transmission 2WD. Its from my father in law and it treated him well and so I hope it does me well too. Fixed the little problems like no brake pedal, door handle barely working etc common Dakota issues. However this one has me stumped.

During the winter he seemed to have an issue with the ECU where the truck wouldn’t run. Took it to a shop and they had it for about a month while they were searching for an ECU that was apparently hard to come by. They ended up sourcing an ECU from a MANUAL Trans Dakota of the same year. He said when picking it up the truck was bucking violently and wouldn’t drive correctly at all. He took it back and they seemed to unplug something from the Trans that make his issues go away. HOWEVER the truck now only shifts 1-2-3 and no 4th, Overdrive button/light on the dash does nothing and isn’t lit up. He said this all started after the new ECU/unplugging the connection at the trans. I checked the fuses and didn’t find anything out of the ordinary.

I havent actually gotten under the truck to replug whatever was unplugged and see for myself exactly what happens when plugged back in but hopefully some of you guys can chime in and give me ideas.

Any and all help is appreciated!!!
 
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Old 04-23-2019, 08:40 PM
93 ragtop
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I have no idea what the difference is, but Rockauto has a listing for your truck, and they do show different part numbers for auto vs manual.
 
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Old 04-23-2019, 08:55 PM
blackbeemer
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Originally Posted by 93 ragtop View Post
I have no idea what the difference is, but Rockauto has a listing for your truck, and they do show different part numbers for auto vs manual.
Nice find. I checked it out and did see the different numbers. I wonder if I can just buy one of these and install it?
 
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Old 04-23-2019, 10:57 PM
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You can just buy the auto PCM and install it in place of the standard PCM.

And guess what controls the OD and lockup? If you said "The PCM", you're RIGHT! And that manual PCM isn't doing it.

You can fake it, however ... there's a kit to replace a venerable 727 (3 speed no lockup) with a A518 ( basically a 727, but with a lockup torque converter and overdrive. Also known as a 46RH.) It's a vacuum switch, two pressure switches, a connector, and some wire.

RwP
 
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Old 04-25-2019, 01:41 PM
glenlloyd
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I'm finding it kind of crazy that all these PCM's are listed on RA as being one year only. It seems very strange that Dodge made such drastic changes to these things that there's basically no cross-year interchange on this stuff.

In fact if I check car-part.com it tells me that 94 & 95 interchange, at least for 3.9L 4x2 AT trucks. Seems odd that RA doesn't show that same thing.

Steve
 
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Old 04-25-2019, 04:37 PM
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They form fit and function the same; but yes, there are code and calibration differences.

How important are they? Like you, I don't think very in each set of years.

88/89 swap, but the code base was completely different in 1989 (they rewrote the software from just about scratch, although they kept the hardware the same … )

90/91 will swap.

92/93 swaps.

94/95 swaps.

87 and 96, well ...

RwP
 
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Old 04-25-2019, 05:05 PM
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Originally Posted by blackbeemer View Post
Nice find. I checked it out and did see the different numbers. I wonder if I can just buy one of these and install it?
Much cheaper options out there. But yes that ecm needs to go. An auto in a manual truck is fine, but vise versa is no beuno.
 
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Old 04-25-2019, 08:42 PM
93 ragtop
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Originally Posted by RalphP View Post
They form fit and function the same; but yes, there are code and calibration differences.

How important are they? Like you, I don't think very in each set of years.

88/89 swap, but the code base was completely different in 1989 (they rewrote the software from just about scratch, although they kept the hardware the same … )

90/91 will swap.

92/93 swaps.

94/95 swaps.

87 and 96, well ...

RwP




Hey Ralph,

You can use any of them on the 87!!
 
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Old 04-25-2019, 11:28 PM
RalphP
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Originally Posted by 93 ragtop View Post



Hey Ralph,

You can use any of them on the 87!!
*dry* With sufficient rewiring, you can use the ECU out of a 2019 Hellcat also. Not what I meant, though.

RwP
 
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Old 04-27-2019, 09:27 AM
volaredon
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Originally Posted by 96360 View Post
Much cheaper options out there. But yes that ecm needs to go. An auto in a manual truck is fine, but vise versa is no beuno.
before 96 it should work just fine. I have mixed and matched trans and computers in Dakotas before and they have worked fine as long as you get one the same year or +/- a year or so, the listing above about what years work in what is pretty much right.
I have also used computers out of Dodge vans and full size pickups in Dakotas before, often same year will be same PN across vehicle lines back then.
but when I put a 94 computer in my 93, no, the 93 didn't like it.... I tried it twice and one was an Mopar perf version, the 93 truck really didn't like that one. I have a 93 brain in my 92 and have had for 60K miles.
 

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