2002 Swap
 

I have 2002 SC1 automatic and the engine is toast. I have a donor car which is a 2002 SC2 automatic. Will the small PCM connector on the car harness be compatible with the DOHC PCM? Will the DOHC harness be compatible with attaching to the bottom middle connector in my existing fuse panel?

Have you checked the 'Swap Guide' here?
https://www.saturnforum.com/forum/sa...ap-guide-9744/

So you're telling the SOHC based vehicle it is now a DOHC vehicle.

As for your specific questions regarding the PCM connections, I've never visually inspected either, so the schematics will have to answer that one. Below is my train of thought regarding this swap.

Use PCM, BCM, wiring harness from dohc donor car
Use tranny from DOHC donor car. Gear ratios are different.
Use wiring harness from dohc donor car

Wiring harness
transferring the wiring harness is a pain in the ass, footage guarantees you that the PCM and PCM and TCM which is part of the BCM I believe will all play nice with each other. The vehicle will think it is a 2002 dohc.

Circuits
The question then comes down to weather the fuses for the dohc are configured the same in the sohc fuse box. Can look at fuses from the top for initial confirmation but will want to pull fuse box and ipjb to ensure power distribution is in fact the same between the vehicles.

Options
options in common between the two vehicles should work provided the wiring to them, the power distribution, and the rest of the circuit matches. May end up with permanent check engine light. If you are in a state where this is unacceptable for emissions, I highly discourage you from proceeding due to the cost of getting an annual waiver.

That covers the base considerations. I just want braindead but I will look at this tomorrow