The tail lights are a 3 bulb setup. The top one for brakes and night running lights. The middle for signals and night running lights. And the bottom one for reverse. The the top and the middle bulbs are the same dual filament type (3057). If one or both of the bulbs are removed from the tail light assy, then the left rurn signal still blinks the 3rd brake light, the top right rear bulb, and the front left. So, is it a tail light assy? It does have electronics because the bulbs plugs are pressure twisted to make contact when twisted/locked in place to make electrical contact. Is it maybe the PCM under the hood next to the relay housing?
Yes, the brake lights still work.