no brake lights

1999 GMC SUBURBAN
5.7L • V8 • 2WD • AUTOMATIC
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DAVID FOSS
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  • 1 POST
I changed the fuse changed the brake light switch center brake light is working switch changed the bulbs on tail light assembly but still have no brake lights?
Nov 30, 2014 at 4:07 PM
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KASEKENNY
  • ✓ASE Certified Mechanic
  • 18,907 POSTS
  • ASE Certified Mechanic
We need to start by checking the ground on the left frame rail behind the bumper. G415 is the ground and if it is dirty then that is going to be the issue.

I attached the wiring diagram below that will help with this. Here is a guide that will help with testing.

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

If this is not the issue, then the most likely cause is the turn switch as the power is fed through this. The third brake light is run through a different circuit so if this is working then the switch is most likely the issue.

Please run through this testing and see the wiring diagram below and let me know what you find.

Thanks
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Feb 7, 2022 at 2:09 PM
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