I also have an 06 lbz silverado LT. I am having this exact issue with my truck as well. No dash cluster lights, no climate control back lights, no 4x4 indicator lights. I have checked fuses, wiring, back light bulbs, and have replaced the 4x4 selection switch, the headlamp switch, and the ambient light sensor. I still have the same problem. I have found the wire that supplies the 12v to the cluster, and am able to illuminate the cluster by sending 12v through this wire. I have also traced this wire to the bcm. I have run several tests, and have found this wire is not receiving 12v from the bcm. This is where I am at this point. Haven't given up, just keep looking for the next step.