My 2003 Honda Accord’s driver’s side brake light does not light up when I apply the brakes, but the light bulb goes on when I turn on the lights. I checked the bulb and it looked OK. Does the bulb have two settings?
Two filaments. The Owner’s Manual will tell you how to replace the bulb.
It sounds like a typical bulb fault. The two filaments can short out one to the other. Just replace the bulb and it should be back to normal. If not we can move on to step two.