I just bought a 2003 suburban and the brake lights won't come on when you hit the brake pedal. I have read every post and youtube video about "no brake lights"
Tail lights work, headlights, fog lights, turn signals, and hazards. All the lights work except the brake lights and the third brake light.
Checked all fuses related to brakes, I changed the brake light switch, multi-function switch, the light switch, the bulbs, and the junction block in the rear. I have no clue what else to do! I need a Jedi master to show/tell/guide me on the way to check a circuit. I assume there is a break on the brake circuit. I have Haynes manual. Not much luck with it. Thank you in advance. I have multimeters, test lights, and a power probe. Any help would be greatly appreciated.

 

I assume you checked the stop lighy ffusein the dashboard (left side). Next step is to test the wiring. You'll need a schematic. Start at the brake light switch under the dash on the brake pedal arm. Use jumpers or back probes to see if you get voltage when the switch us activated. This will split the wiring in 2 and tell you which side of the circuit (i.e. before or after the brake light switch - BLS) to check next. For example, if you do not get voltage when BLS is activated, then thd problem is between the BLS and the battery. Verify that the brakd lights come on if you supply power to the BLS output wire.