when my headlights are on, my taillight goes out when i step on the brakes.
Check you bulbs in the rear. I believe they have double filaments. You may have one of them blown out on both sides. If not, you will have to start tracing wires. Something has grounded out or fused together. It's a major pain. The wiring harness runs under the bed, and once salt or rust gets in there, it will raise havoc with the electrical system. I have had to do it many times. Had an '89 4x4 on the east coast. Had to rewire the rear every couple of years.
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