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I'm also at a loss as too what the Start Stop changes in the Engine? PCM, TCM, starter and battery wiring, yes....
But as far as the engine is concerned it "seems" to be the same, its just shut off when you come to a stop and then the trans is shifted as the PCM starts the motor to start driving again when you press the pedal....

This is what I read on Wikipedia....
Pentastar upgrade
For 2016, FCA released an updated version of the 3.6 L engine for the Jeep Grand Cherokee and Dodge Durango. This engine now featured two-stage variable valve lift (VVL), a cooled EGR, a new intake manifold, new fuel injectors, and new ignition coils. It also features upgrades to the variable valve timing (VVT) system, an increased compression ratio (11.3:1), lower internal friction and lower weight. These improvements help to increase power as well as efficiency.[8] The new version, however, has lost its flex-fuel capability.
So a 2015 engine and vehicle has no VVL, and a 2019 will have VVL....
That means there are sensors, solenoids and circuits and controlling software in the PCM to control the VVL....
No, unlike MDS, you can't disable VVL, if you do, then the engine will running a minimal lift/duration cam that likely will only make half the power if not less.....
And to move the PCM and wiring over is also going to turn it into a franken car with all sorts of ramifications, conflicts and problems to resolve......
Different fuel injectors, ignitions coils and perhaps even the intake manifold could mean differences in the PCM....

Even doing a franken motor might be impractical, i.e. take the 2019 motor and try to put it into the 2015 configuration with 2015 parts..... meaning you'd need the cam and lifters (aren't your cam and lifters toast on the 2015)? this still probably won't work because they changed the compression ratio and even the block (if its lighter with less internal friction), compression ratio changes require changes in the cam and tune, and you're sticking a cam and PCM with a tune for 10.3 compression ratio version of the engine in a 11.3 CR version........
 

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Discussion Starter #22
Understood, pardon my ignorance here but I was thinking I would swap the entire motor, PCM and wiring harness from the ‘19 to the ‘15. Along with the associated sensors and what not.
I could even bring over the transmission as well if needed to make everything work together smoothly.
My simplistic thinking is that I am then only concerned if the dash electronics are the same right? And if they are wouldn’t that work in theory?
 

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2015 WK2 Overland
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I would do just the opposite and bring as little as possible over. You'll have differences with the steering as well - the 19 will have electric steering, the 15 will have the electro-hydraulic. That will be included in the engine bay harness. It will have a ESS button but that is all CAN based, there won't be a dedicated wire for it. It's hard to say if the PCM/TCM would interpret the shifter differently. I know the starter is different/upgraded for the ESS.
 

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Understood, pardon my ignorance here but I was thinking I would swap the entire motor, PCM and wiring harness from the ‘19 to the ‘15. Along with the associated sensors and what not.
I could even bring over the transmission as well if needed to make everything work together smoothly.
My simplistic thinking is that I am then only concerned if the dash electronics are the same right? And if they are wouldn’t that work in theory?
That's the problem, no one really knows, perhaps the designers, good luck getting them to give you the time of day..... ....because they can't tell you off the top of their head, they're not going to put in the work to review everything, and the current liability environment for manufacturers the lawyers would bar them from telling you anything anyway....

It will be a franken car, there are going to be unanticipated problems and gotcha's, the key is will it be just a few that can be practically overcome or will there be many with some that are not practical to overcome.....

One I can think of right away is the immobilizer, it needs to check VIN# across several different modules, and you're going to have different VIN#'s in those modules, so it won't start. You can get a tool that can write VIN#'s to the modules, that could be easily remedied, most electronic tools can't do this.... ....you could just have it towed to the dealer and have them write the VIN#'s....

And that is just the ones I can think of, I'm sure you'll run into others.....
 

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2019 Grand Cherokee 3.6 Limited.
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Understood, pardon my ignorance here but I was thinking I would swap the entire motor, PCM and wiring harness from the ‘19 to the ‘15. Along with the associated sensors and what not.
I could even bring over the transmission as well if needed to make everything work together smoothly.
My simplistic thinking is that I am then only concerned if the dash electronics are the same right? And if they are wouldn’t that work in theory?
It's not just the PCM, there are lots of other control modules in your Jeep. These modules all talk to each other and if they don't see the correct information sent and recieved they could play up and cause all kinds of problems. I'm not saying it can't be done but its going to be a bit of a minefield, theres just no way of knowing how it would turn out. Any future problems on your vehicle could be a nightmare to fix.
 

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It's not just the PCM, there are lots of other control modules in your Jeep. These modules all talk to each other and if they don't see the correct information sent and recieved they could play up and cause all kinds of problems. I'm not saying it can't be done but its going to be a bit of a minefield, theres just no way of knowing how it would turn out. Any future problems on your vehicle could be a nightmare to fix.
AlfaOBD would probably be able to handle changing everything but the number of options and combinations is endless (not really but huge). It could take ages to get everything to work. But hey, if you have the two side by side, pull the harnesses and start comparing. What can it hurt. :cool: Someone has to be the Pioneer on these things and start doing crazy stuff with them. Look at all the old Wranglers and XJs buzzing around with crazy mods. Y'all too conservative!
 

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Yeah, I’m out then. I’m not willing to spend the time dealing with all the little garbage.
Yea, you've got another project your working on....

And that may have been a way more concise way to get my point across.....

Its very possible this project will drag on months a year, with expenses, trying to solve all the little incompatibilities that are going to come up..... ....its even possible you may never get it working well at all.... ....are you willing to bite off on that kind of risk....

Sounds like you're not....

And sorry, wish I could tell you for sure, but it looks like no one has done this and thus you'd be the first guinea pig, it might have been pretty easy.... ....but I think everyone posting is going to agree, chances are, its going to be hard and a big risk it turns into a nightmare project....
 
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