I have a 2002 silverado 1500 HD 6.0L 4x4. Recently noticed my driver side brake light and 3rd brake light arent working when i press the brake while the truck is running, keep in mind while the truck is off all the break lights work fine it's only when running the driver side and 3rd break light don't work. While the truck is on both the running light on the back work fine. I changed the bulbs, I've changed the brake switch, I've tested the socket for power and cleaned it for any corrosion. Any advice on what I could check for next? Btw the ABS and Brake lights on the dash are lit up, they've always been lit up. Haven't had any problems with the brakes stopping.