GM Repair Problems? Ask GM Repair Expert Now.
Start by testing for voltage on the orange wire at the switch. If you have voltage there and jumping the orange and white wires together does not make the brake lights come on then the problem is likely in the turn signal switch. Power goes from the brake switch, through the turn signal switch and then to the rear bulbs. (turn and brake uses same bulb filament at the rear) Since the turn signals work we know that the bulbs and wiring from the turn signal switch are okay.
These other wires may be for TCC unlock signal. The brake light wires are definitely Orange and White. Look around under the dash to see if the connector is unplugged from the switch.
You are very welcome. Glad I could help.