A problem literally just happened on my 08 truck. I wasn't even using the lockers, then the Fr. & Rr. locker light started flashing and the Rr. only light wouldn't illuminate during the standard key on bulb test and then when I tried to engage it, nothing would work. I scanned for codes and received a C143B code, then I followed the factory service manual procedure and the conclusion from that resulted in a condemned final drive control module/smartbar. I started looking up prices and figured I would be hardwiring my lockers after seeing how much it was.

After the shock wore off, I looked closer at the schematic diagram and decided to go one step farther and test continuity on all the wires between the switch and the FDCM and found that I was lacking contact on several of the wires. Then I started inspecting the harness for damage but found nothing. I looked at the diagram again and found that on my truck there is a connector in the harness between the two components (C137), searched the manual and found the location under the dash at the left kick panel, in front of the parking brake. I looked under my dash and found it and it looked connected, but when I tugged on it, it came unplugged.

I pushed it back together until I heard it click and then retested all the wires for continuity.

YES!!! Put everything back together and turned the key on, all the indicators illuminated correctly and no flashing lights. Drove it to some dirt to test the lockers and smartbar and everything functions like normal.
I just thought I'd share this with you, cause I know you're dealing with the same issue on a 3G. Yours may be the smartbar, as the dealer says, but it wouldn't hurt to check C137. Good luck!

- Connector C137 is the smaller one with all the yellow wires in the middle of the picture.