Body control module location

It is under the center console mounted to the floor. 18 in the image. What issue are you having?

It will not be below the carpet, but it is buried under a bunch of components. It is just a simple aluminum box with a couple connectors on it.
For a door lock issue the BCM is not involved. That is a stand alone module located behind the left rear 1/4 panel trim in front of the wheel arch. However, as the problem does not effect all the doors the module is not the issue. It sounds like you have a bad door switch and possibly a bad latch. Which door(s) are working okay and which are not?

This is not the lock/unlock door switch it is the door lock module which is in the rear of the truck. It controls all of the lock functions. The switch I referred to would be the jamb switch that turns on the interior light and door chime. If it does not matter which door you open/close but the chime/light issue is still a problem then it is likely the jamb switch input on the lock module.
As they all lock it is not a power problem. Instead it is an issue with the unlock circuit (the white wire) on the diagram. As it carries the unlock signal from the switches to the module. If the doors all lock from each switch but will not unlock then that wire or the module itself has an issue. Most likely would be a bad connection or break right at the module. A bad connector at that module could easily cause all of your issues.

The BCM does not connect to or control the locks in any way so it cannot be the problem. The locks are only controlled through the door lock module and the switches at each door. If you have the remote entry option that is another add on but it would not cause your problem unless you can lock/unlock with the door switches but not the remote. That is why I attached that wiring diagram. It shows the module and it's wiring. Lock uses power through the switches to the light blue wire. Unlock uses power into the switches and out on the white wire. As you have the ability to lock the doors the power feed into the switches is working and the light blue wire to the module is good. However you cannot unlock the doors, if it was only that you could not unlock the doors at say the passenger front door, then I would say check the switch. However you say you cannot unlock from any door. That points at the module as all of the switches are wired in the same circuits.

It will be under the 1/4 panel trim. I would first test at the connections for the wires before removing or disturbing the connector. If you move a switch to unlock, you should see battery voltage on the white wire in the connector. Lock will put voltage onto the light blue wire. That will tell you that those circuits are good from the switches to the module. Then remove the connector and see if it is corroded or damaged.

Click on the image on this page, then click on the image that loads. Should make it very large.

Power comes from three sources. The cigar lighter fuse (13) the gauge fuse (4) and the power accessory circuit breaker. Check all of those first.
The power goes to all the parts on the orange wires.

Nope you did not mention that. That makes it a lot different. If there is power to them in both lock and unlock then you need to check the actual power available at the lock. The easy way to do that is to use a large draw test light, like a headlight or similar bulb. Just connect it in the place of the two actuator wires. Then hit the switches in both directions, if it lights up bright both ways the actuator has failed, not uncommon on GM's of those years.

That module is only there if you have remote door locks. If you do not have key fobs there will not be a remote module.