CHMSL 3rd brake light stays on after truck turned off

[silverbirchmetallic]

I have a wierd intermittent problem with my 2009 Silverado. The 3rd brake light stays on some times--this is random. I can get it to shut off sometimes by starting up the truck then shutting it off. I have looked at wiring diagrams, and it seems that the CHMSL gets power through a PCB relay under the hood from the BCM via a blue wire X5/5. What I don't understand is that some wiring diagrams show a fuse 49 under the hood that is after the PCB relay and before the left I/P junction block. I do not see any wiring diagrams showing the 15A relay in the left I/P (fuse #12). Can someone help me with the correct wiring diagram? Any idea why the light is staying on? Thanks!

[silverbirchmetallic]

More info..just replaced the stop light switch and that did not fix the problem. However, I can get the light to go out by turning key on (or starting it, either one), and slightly pushing the brake pedal. I hear a clicking sound like a relay is cycling when I push the pedal. The 3rd brake light follows the clicking sound. It almost seems like a pedal adjustment, but I don't see any way to do that. Any advice would be appreciated. Thanks!