​what do I need for the engine swap I swapped out my 2.5 engine for a 3.5 engine but I cant get it to run or function correctly using the 2.5 computer it cranks up but doesnt drive fast or function correctly and when I put the 3.5 computer in it doesnt crank at at all it doesnt turn over

 

Probably needs a dealer reflash.

 

I have called the dealership 4 different times and they always tell me that they do not do any computer flashing/relearning/reprogramming they only fix your existing computer if its broke and rewrite it back to the vin of the car and that's the problem the vin of my car would give only the 2.7 info and update but I need it to run and have the software of the 3.5 engine that is not installed

 

@jkeaton I have called the dealership 4 different times and they always tell me that they do not do any computer flashing/relearning/reprogramming they only fix your existing computer if its broke and rewrite it back to the vin of the car and that's the problem the vin of my car would give only the 2.7 info and update but I need it to run and have the software of the 3.5 engine that is not installed

 

LMAO....didn't really research this one beforehand? So no, unless you have a close friend in the service dept they absolutely will not do that for you as you have changed the configuration of the vehicle. The PCM/control system for the 2.7 is different than the 3.5. Even worse, 2.7 only ever came with the 42RLE transmission (4sp) while the 3.5 came with both the 42RLE and NAG1 (5sp). It runs like **** on the 2.7 computer because it isn't designed for the 3.5. It doesn't run at all on the 3.5 computer because these cars have SKIM keys and you just blindly plugged in and energized the bus with a different and non-matched PCM to the SKIM; good chance it may have locked that PCM already. Also, 1) the harnesses are different and it is most likely not getting the correct inputs it needs before it will fire and 2) you most likely tried to use a PCM from a 3.5 car that had the NAG1; NAG1 car uses a separate TCM for trans function. 50/50 shot from what I've seen that it will start at all with the trans inputs removed. Most likely because of the SKIM issue though. I will assume you're using the original 2.7 engine harness plugged into the 3.5 engine; if that's the case you need to find if you can get a 2.7 PCM custom tuned with basically a 3.5 tune. If you actually tried to use the 3.5 harness, you need to find the PCM for a 3.5 with the 4sp, then have it installed with a new SKIM (those modules can only be initialized to a PCM once) and have your keys programmed to it.

 

@Magnoom thanks for your reply and he said he used the 3.5 harness …… and what do you mean by (then have it installed with a new SKIM) .. do you mean actually buy a brand new skim module ??

 

@Magnoom if I get a 3.5 pcm from another car at the junkyard it will have that car skim information already stored in it so what would getting a new skim do and where do they even sell new skims for purchase that haven't been used yet im just trying to understand better ??

 

the 3.5 harness is installed on my car

 

You're not getting it. You CAN'T just go get another random PCM at the junkyard. It has to specifically be one that has engine AND trans functions. Each SKIM and PCM are initialized to each other. If a PCM gets an improper SKIM signal, it won't run. SKIM gets the signal from your key. The SKIM in your car is initialized to your 2.7 PCM. It cannot be initialized to another PCM, which means you have to get another SKIM to mate with the newer PCM you wish to install. The junkyard PCM you desperately want to go get will be mated to THAT car's SKIM, not yours (and cannot be mated to your existing one, if you try you'll lock the PCM). Further complicating things is that both modules have to VIM match the car or it will cause trouble. SKIM = Security Key Interface Module. They sell them new. Go find one.

That could be good or bad. What was the car you took it out of? 4sp auto or 5sp auto? Or did you not bother to find out.....

I need to understand your thought process here....did you do any research prior to this or did you just figure since it was the same platform you could just drop it in and everything would be good to go?

 

@Magnoom an old friend of mine did the swap for me … so question what if I went to the junkyard and made sure it was the right dodge magnum with the same 42rle transmission and took the (computer) from it and the (skim module) and the (key ignition) and got the keys for the car at the junkyard would I be ok then