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Discussion Starter · #1 ·
I'm currently working on a swap from a 2002 3.9L AT 2WD quad cab to a 5.2L out of a 98 ram. I've been scouring forums and cannot obtain a straight answer as to what I need to make this work correctly. I'm adding the two injectors and adapting the sensors to the 3.9 harness.

I'm also changing the transmission from the 42RE to the 46RE that was behind the 5.2.

What pcm do I need to be searching for? A 2002 5.9 quad cab? Just a 5.9? Will a pcm prior to 2000 work?
 

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Discussion Starter · #3 ·
I've read conflicting posts, does the trim level matter when selecting a pcm? I've located a vin for a 2002 5.9 RT AT. My truck is a SLT quad cab though. Should that effect anything negatively?
 

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2004 dakota 4.7l cold air, cat back, 545rfe trans detroit locker on a 9.25 265/70r17
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I've read conflicting posts, does the trim level matter when selecting a pcm? I've located a vin for a 2002 5.9 RT AT. My truck is a SLT quad cab though. Should that effect anything negatively?
Sub model shouldn't matter. Transmission might. Before 2005 the pcms weren't vin specific as far as I remember.
 

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Discussion Starter · #5 ·
So my 42re is garbage too, I have the first 3 gears and nothing else. I was going to swap the trans too, what I got (I believe) is a 46re (considering that was standard for rams). Everything I've seen so far Looks like it will be a plug and play. You wouldn't happen to know if that would be true, would you?
 

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2004 dakota 4.7l cold air, cat back, 545rfe trans detroit locker on a 9.25 265/70r17
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So my 42re is garbage too, I have the first 3 gears and nothing else. I was going to swap the trans too, what I got (I believe) is a 46re (considering that was standard for rams). Everything I've seen so far Looks like it will be a plug and play. You wouldn't happen to know if that would be true, would you?
Shouldn't be to hard although they did make changes in 2000 to several things. As long as you have the pcm that ran the engine and trans from the ram you shouldn't have too many issues. I'd swap out the wiring harnesses too.
 

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Discussion Starter · #7 ·
I don't, I only got the motor and transmission. I found this other thread regarding transmissions:
Trans question 42RE vs. 46RE - 99 Dak
All I was going to do was repin my injectors, add the two missing injectors into the harness (currently ev6, need ev1) and get the 5.2 sensors that have the correct connections for my 3.9 harness. The only two holdouts I have are the pcm and transmission compatibility. I found a guy local to me who has spare parts for the motor, so I'll have the plugs and sensors by tomorrow.
This is my first swap, in my first truck (I've had it since 2011). Originally I was going to LS swap it but I realized how much would have to change to make that happen and I don't have the pockets deep enough to do that. It was my daily up until the motor completely bought the farm about a week and a half ago.
 

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Discussion Starter · #9 ·
I was really after first hand information, maybe im missing something... it seems too easy... but you've been very helpful, thank you! I'll post here again after it's all said and done, or maybe I'll hit it up for more questions. Either way, thank you
 

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I work for one of the biggest part suppliers in the industry, and i can tell you that there are 6 different PCM part numbers for my 2002 and they DO require flash re-programming (VIN and Miles) on or off the vehicle. The normal way to determine the one you need is to match up the OE PCM's part number. In your case, thats not as important as these key things that do matter: Engine, Transmission, Emissions System, Mileage, VIN.

I've also personally done PCM replacements and Instrument Cluster replacements. Vin and Mileage matter. The data for each are stored BOTH in the PCM and the Instrument Cluster. If the PCM has a conflict with the same data stored in the Instrument Cluster, it will go into Limp Mode. Example: forget the motor swap for a moment. Pretend your Dak has 200,000+ miles on it; you could go to the scrap yard and buy a instrument cluster out of a Dak with only 70,000 miles on it and swap it into your truck and put it up for sale. Nope. Believe me, the manufactures have thought of this, and if it were that easy to manipulate the mileage on a vehicle, everyone would be dong it. This isn't the 1960's. If you try that, the mileage (and VIN) stored in the PCM will have a conflict (a non-match) with the miles stored in the cluster and the truck goes into limp mode. Its the same with a VIN conflict.

In short, some flash re-programming will be needed so that your cluster and PCM have matching VIN and Miles, and you need to get the PCM that matches up with your Engine, Transmission, and Emissions System combination.

Yes, obviously, most the emissions system comes over with the engine, but what about your exhaust? If your Dak is 49 state federal emissions equipped and thats the cat converter still on it, if you match it up with an engine and PCM from a California emissions equipped engine and PCM, you re going to have CEL (Check Engine Light) issues. The software on the California equipped PCM will be looking for a higher level of emissions performance than your 49 state converter can provide and you will end up with P0420 codes (Catalyst System Efficiency Below Threshold).

You can find the emissions info on a white 2x5 inch sticker stuck to the underside of the hood of your DAK (assuming it still has the original hood). There is a paragraph on that sticker that will tell you the emissions its equipped with. There are only 2 systems; "49 state Federal" -or- "49 state Federal AND California".

The easiest thing I can think of is; get the Engine, Transmission, Trans Control Module (dont forget that) and PCM all from the same donor truck. However, the PCM will need to flashed to match the VIN and Miles of your DAK. Check the emissions info sticker under of the hood of your donor truck (assuming it still has the original hood) and hopefully it matches your Dak. Otherwise, you may also need to swap a cat converter onto your Dak that matches the emissions of the donor Engine/PCM.

You may also need to match up the O2 Sensors to the right emissions system as well.
 

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Discussion Starter · #11 ·
It says it conforms to epa regs at all altitudes but nothing stating federal or federal plus California, so I'd assume federal. As fat as the tcm, I did not get anything else with the motor or transmission aside from some accessories. All I've been able to find is reprogrammed pcms, not flashed specifically to what I'll have. This truck has just under 180k on a 3.9L with a 42re trans.

What you're saying is basically I'll need to dig around and find someone who can custom flash the pcm (or one thats compatible, which i cant find info on) to be a 2002 RWD with a 5.2L and a 46re, get a wiring harness for the trans and engine, and a tcm just to get this working?
 

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Flash/reprogram are the same thing. Often there are shops or mobile techs who can flash these modules, but as far as i know, most can only do it after they are installed in the veh. When ordering a PCM from a rebuilder, like A1 Cardone, you can give the vin and miles to them and they flash it before sending it to you.

as far as the TCM, i dont know if they are cross-compatible with different trans Units. I’d guess not. For example the 45RFE (aka 545RFE) matted to my 4.7 is not cross-compatible with the 42RE or 46RE. I’m not as familiar with anything related to the 3.9, 5.2, 5.9 engine family as they are older technology vs the 4.7 design, and modern hemi’s, that were designed to replaced them.

As for the wiring harness, im not 100% sure, but Chrysler (aka: Daimler-Chrysler and Chrysler LLC) were known for using common wiring harnesses in the late 90’s and through the late 2000’s. So… best guess, you should be ok there.
 

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What made you decide to go with a 5.2 anyway..? Honestly, they are a pretty gutless, heavy and old pushrod design. BTW, the only difference betwern the 5.2 and 5.9 is the heads; and they can be swapped.
 
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