Hello i have a 2000 Sierra extended cab 4x4 and when i press my brake pedal my tail lights all frig up does the same when i turn the headlights on. By frigging up i mean everything flashes. I have replaced all the sockets and wiring from the junction box under the body, even tried another on of them but still no change. Can anybody help me ? I know it is a common problem cause i see a lot of trucks around here doing the same thing....

Thank you