Third Brake Light Not Working and Has No Power?

2007 GMC YUKON
208,000 MILES • 5.3L • AUTOMATIC
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2007GMCYUKON
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3rd brake light out no power .. check fuses all the fuse in both inside and outside boxes just because i was there anyways. Check light with direct power to it lights fine . Check for current to light im getting nothing with brake pressed or not pressed its light blue wire positive and black wire negative. check pigtail wire harness also nothing... Brake lights work perfect blinkers work fine reverse light all good plate lights good also. the 3rd brake light wire runs along the inside drivers side could the brake switch cause this ? also seen someone mention the parking brake switch? another said bcm . I have a pretty good understanding that BCM send a signal to light it up but does it go thru the brake switch or direct ? I know its on its own power source is why everything else works. just stumped on this one any help appreciated dont want to start buying all kinds of parts and still at square one. Thanks guys
Jun 28, 2026 at 5:56 AM
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STRAILER
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I got you covered, yep this problem is pretty straight forward, the BCM or wiring from the BCM is bad. Here is a guide to help you check the wiring if needed to confirm the problem and the wiring diagrams for the center high mount brake light so you can se ehow the system works.

https://www.2carpros.com/articles/how-to-check-wiring/

Check out the images (below). Please upload an image or a short video in your response, so I can see what's going on.
Jun 28, 2026 at 5:26 PM
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STRAILER
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Sorry here is the diagrams,
Jun 28, 2026 at 5:27 PM
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2007GMCYUKON
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Thank you for the diagram i was wondering if it went thru a switch like alot of people mentioned... i didnt think so ALSO on my model it was confusing me prior kept telling me to look for CHMSL fuse its not on mine its the STOP LAMP fuse i have nothing and i looked a few times that list CHMSL or VEH CHNSL that was fun . Next step will run a wire from the bcm to light direct to see if that eliminates any breakage along the way replacing the lt blue wire usage coming from it. if not bcm replacement time its sounds like ..
Jun 28, 2026 at 10:01 PM
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STRAILER
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Yep the CHMSL or VEH CHNSL is on older vehicles, I like the wire idea. Let me know.
Jun 29, 2026 at 2:00 PM
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2007GMCYUKON
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CHECK IT and yes BCM issue so i did what i should of first ran a wire off blue wire on left brake light that lights up brake light and done tried to do fix the other way but way too much money to spend . my first concern was the blinker might set off 3rd brake light but then realized there 2 separate bulbs and connections so no issue and also since its an led light watts should not be an issue on draw. well on to the next issue but thanks for the help it made things alot clearer to see the way it worked .....
Jun 30, 2026 at 5:55 AM
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STRAILER
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Sweet!! So it must have had a broken wire. Glad you could get it fixed, thanks for letting us know. Can you please leave us a rating?

https://g.page/r/CZdEnyCkGgm6EB0/review

and

https://www.sitejabber.com/reviews/2carpros.com

Thank you!

Jun 30, 2026 at 2:47 PM
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