I have a 2003 neon sxt. We got a motor from someone who claimed it was out of a 2003 neon sxt, but we noticed there were a few differences. Mainly, the crank sensor is on the opposite side of the motor. Since the plug was the same, I modified the harness (without cutting any wires) so the plug could reach the sensor. After the motor was put together and put back in the car, I got a code for irratic crank sensor. The car would not start and would not fire at the plugs. I got a new sensor, but that did not work. What I am trying to find is a flash update for the engine ecu to overwrite the existing 2003 crank sensor protocal in my ecm to the 2002 crank sensor protocol. Is this even possible?? In my mind it's as simple as deleting a program on a computer and installing an older version of it, but I have this sneaking suspicion it is not. I did some reading and found that wikipedia says "the 2002 engines generally are not compatible with the 2003 neons". The word "generally" leads me to believe a swap is possible, but I am not sure what is required to make it a successful swap. Please help. Any insight would be great. Does anyone have any idea how to obtain parameter modification software for the dodge neons?? It's as simple as a device driver for a computer...please help.

 

2003+ NGC computer systems are a whole different beast from previous years. Nothing is really simple with them.

Here are some quotes from others who know a bit more about this than I. This was about putting a 2004 engine into a 2002 Neon:
Essentially, you either need to get a pre-03 engine or swap over the entire 03+ wiring harness and computer system. The two different engines can be swapped (referring to your "generally" quote) if you run an aftermarket system like Megasquirt. That though, you have to wire the entire system up yourself IIRC, and then tune it properly.