Where's the ECM?

[Darrinswait]

2000 I30...getting ready to replace the ECM, but where the heck is it? I know that I need to make sure that I replace it with the correct ECM. From what I understand, there are two different ones...how do I tell which is which? Gonna put a used one on to see if this is the problem, then might get a rebuilt one.

[Towncivilian]

I'm not sure whether the ECM itself lists its part number on the exterior of it. My Pathfinder's ECM doesn't appear to, at least from the side I can see when I put my head in the driver footwell.