body control module

[RotorRob60]

I have a '97 Sonoma, originally with a 2.2L engine. I have replaced it with a 4.3L V-6. Where exactly is the 'Truck Body Control Module'? The unit on top of the heater seems to be an actuator or servo of some sort; not what I thought the TBCM should be. I need to connect a serial data class 2 ( yellow ) wire to it from the 4.3L's VCM. Thanks!