Why does my headlights come on and stay on?

Hello, This is likely the headlight switch (multifunction switch), but could also be the body control module or headlamp relay. The headlamps are allowed power at all times because they need to function sometimes when the key is not in the ignition. If the automatic headlamp circuit (which should be disconnected with the key off) gets power erroneously, it will turn the lights on every time it gets dark, and may even turn on the daytime running lamps when it is light out. Check the headlamp and daytime running lamp relay, then test the mutifunction switch you use to turn the headlights on and off.