Should be the same harness. The only difference is the trans harness, whether two or four wheel drive. Most newer harnesses are plug n play types, so unplugg from computer and from the sensors on the block if you want to change harnesses.

 

The reason i ask is because the 2003 pcm is unique and if i switch to a 2004 hemi engine it might start throwing codes and not running right? Do i need to change that for sure? because different people are saying yes and some no. and so the harnesses will direct fit from my 03 hemi into that 04 hemi?

 

Agreed. There is no difference between the motors themsleves. There is nothing wrong with your pcm and wiring harness. If a connector from your original wiring harness does not match up with a part on the new engine, just swap said part from your old motor on to it.

Should be very easy. no need to mess with new pcm's and harnesses

 

an 04 motor will plug into a 03 harness no problem

 

I am sure others can answer this, but can't you tune easier with an 04 PCM??

The OP originally started a thread about running a twin turbo set up on this new (to him) motor.

nateroach

 

I believe there are more transmission tuning options with 04+ since they have just the PCM for the engine and transmission. 03s have a PCM & TCM and the TCM isn't tunable (to my knowledge) from a handheld unit.

 

Thats true on the tuning issues with the 03 and every guy out there with an 03 who is wanting a radical engine wishes he had an 04+ PCM. Even mine with an 04 have limited trans support. Im going to an 05 PCM setup.

 

You can tune easier with an 04 PCM, but you have to some major wire work to make it work in an 03 body/harness. Simply depends on how much work you're willing to do.

 

Weed -is right about the 03' .. Although 04' has more to offer with programmers..05' has more and 03 has almost none..BUT if you're going to stay stock , you don't have anything to worry about..I have listed all pinouts 03' - 04'..with 03' TCM as a stand alone unit.on my thread called"Dakota Hemi Swap!!With pics!!!Wiring pin-outs start on page 10..
On the 04'-up the TCM is built into the ECM..C-4 plug..The difference between the 03' and 04' Motor is the EGR. 03's don't have one..
My 2001 Dakota Quad has a 2004 Motor and trans, While my Harness and computers are 03'..It would be better if you could use the 04' Harness that came with the 04' Motor and transmission, to do your swap..But if you have to use the 03' Harness you can...

 

My 2004 Ram 2500 5.7 Hemi dropped a valve at 120,000
had a new engine installed at a Dodge dealer. before problen I was getting from 15 to 20 mpg, now only get at the best 15 mpg.
Was the 5.7 hemi ina 2500 different from later model 1500 engines
2005 and up and was the 1500 engine different from the 2500
I suppect they installed the wrong part # engine!