plugged into a 12 pin black connector X13025 below RH side of rear seat.
Pin assignments are:
1 Red/Gray: F47 fuse hot at all times
2 Violet/White: F18 fuse Hot in accy, run and start
3 Brown/Orange: Ground (Ground post X490)
4 Brown/Gray/Yellow: Driver's door (0V open)
5 Brown/Blue/Yellow: Passenger's door (0V open)
6 Brown/Violet/Yellow: Rear doors (0V open)
7 Black/Blue: Anti-theft horn
9 White/Red/Yellow: General Module pin 7
10 Blue/Red/Yellow: General Module pin 16
11 Red/White: Trunk lid switch (12V open)
As you may see, location is not exactly what you said, but wire colors should help you identify the plug, as door signals are wired as stated. Also you can test with a meter pin voltage behavior according to signal identification.
Anti-theft horn is the same one used by OBC, connected at X372, 2 pins gray connector at rear RH side of engine compartment.
Not sure what GM signals are for, but guess they are keyless related (actuator over GM Central locking).
Javier