I had the same problem on my 91 K1500. The most common reason rear lights of any kind will fail is rotted wires. They run through wire shroud from front to back along the inside of the frame to the left tail light. Running this way leaves them exposed to the elements. Check along the run for rotted, broken or degraded wire. Most spots would be at anchor points, junctions, etc. If you do find a faulty wire, just run a new one from the engine bay to the back and splice it in. Its a cheap fix and takes WAY less time. If it was me i would clip the wire at the tail light harness, about 4 inches back, then move to the engine bay and look for the same wire there. it will most likely be beside your brake fluid assembly, in a cluster, entering the firewall. Find the wire and clip it about 4 inches back too. Solder and shrink tube the new wire to these pigtails and give it a test. If you are unsure of the wire color associated with brake light function, you can access wiring diagrams online, but be warned, chev/gm have...