Hope it's clear enough:

 

I just went out and checked my 2011 LT. Either the SS is completely different, or my "book" is WRONG. Stop Light is #9 at the BCM (passenger side, inside the car). db/sb's diagram is correct, but you have to look closely. I don't see a CHMSL relay on mine either.

But, thanks for making me look, every one of my relays were loose one was almost out.

#9 under hood is a diode for the A/C clutch.

 

OH, and the Cruise Control probably won't work with the additional stop light hooked up.

 

My 2011 diagram shows the CHMSL relay to be right beside the under hood fuse block mounted on the fender. I checked my car and there it is with no markings of any kind. The lt blue wire is there as well.

 

AH HA! Black box, hidden in the shadow under some black wires. It does exist!

 

I’m having this issue with my 2010 1LT - suddenly no light. But in my case, I did nothing to change the circuitry.
Is there a different diagram for this year with different fuse placement? It’s not in the large fuse box under the hood. Could this year’s 1LT have a totally different 3rd Brake Light placement?

 

No it should be in the same place.

 

What is "the same problem" from 2014? The fuse is on the BCM not under hood. Post #12. Relay is on the driver side fender. See post #14.

The 2010 circuit is a bit different to the one posted in #11 here is a pdf, the wires marked 1 & 2 go to the ECM and TCM to control the cruise control.

exterior lights.pdf

 

thank you for that diag. I attempted to trace the issue, and it turns out the ground wire under the right tail light had somehow lost the ability to ground well, which in turn had caused the relay fuse (the small black box on the left fender) to burn out. I re-soldered the wire, then covered with Vaseline and electrical tape, then went to Autozone and got the compatible Duralast relay fuse, and works perfect now. Here’s a pic of the OEM part

 

this was the route of the solution for me. However, it took a fuse tester and voltmeter to figure out that it was the ground. Thanks again for the diagram. Would have never found where the ground wire was without it!