Alrightie, seems I'm out of luck on this one:
1: I've installed the drivers for the virtual COM ports on my laptop and set it up.
2: I've installed the UniDiag software on my laptop.
3: I connected the cable to my laptop's USB port, the other end to the 3-pin cable and the 3-pin cable to the only matchable connection I could find inside the car.
4: I connected the red wire to the positive terminal of a spare battery I had standing around in the garage.
5: I turned the ignition on and started the UniDiag.
6: I went to the Connect tab and chose "5 baud init", but no COM port shows up in the left hand drop-down list, only some odd number looking something like "0x00000043" or something of the sort.
I tried starting the communication regardless, and though it seems to "think" for a while, nothing further happened. I tried typing in "COM3" (the port I assigned the USB port to) manually, but when I tried starting the communication I got some log file error. I then tried changing the assigned COM port to 5 and retried the whole procedure with the same results.
Now, I do have some theories about why this isn't working the way it's supposed to:
1: The connection between the battery terminal and the red wire is bad.
2: I've hooked the 3-pin connector up to the wrong connector inside the car. My car is LHD, and there are no cables whatsoever in the location shown on the picture above (seems to be somewhere around the accelerator pedal) except for a large white thingy.
I tried looking around for other similar connectors on both the driver's and passenger's side, but only managed to find one underneath the driver's seat.