by MalibuJack » Sat Feb 24, 2007 6:44 am
You'd be surprised.. Many of the ECU's are identical for all of the models, but the wiring from the car to the ECU varies, which is why roms are unique to specific models.
This bit of information isn't really all that useful or surprising, BUT it means that you have to be real careful about swapping roms around. There are some that might work, but due to the trial and error, and the possibility you can do harm, has limited how much experimenting with rom interchange there is between different cars.
As stated above, if sensors or inputs are different between two models your looking at, then you can be sure the roms will not be compatible (either it won't run, sensors won't work right, or you can damage something)
a good example is the 2003-2004 USDM Evo, there's a good chance that any rom from those two years can be used on any other 2003/2004.. But a 2005 has slightly different wiring (No Intercooler sprayer for example) and some other changes, and a 2003 rom on a 2005 may not work properly. (I'm actually not sure if anyone has actually tried this extensively)
But to point out, the 3rd gen ECU's (2001-2005) are for the most part physically the same, different generations have slightly different hardware internally, but you can find a rom that will be compatible with your car and it should work as long as you didn't lose your immobilizer.