Hi, I have a problem where my brake lights stay illuminated brightly (both sides in the rear and the third brake light in the rear window) whenever my automatic headlights come on at night. So whenever I drive at night, my brake lights are always on, not just the dim running tail lights. I did some testing and found out that if I press the brake pedal before my headlights turn on, it also illuminates my front corner lights but not my actual headlight bulbs. I assume that there is a relay or circuit board somewhere that controls the headlights and brake lights, which probably got fried when I got LED replacement tail light bulbs a month or two ago. I checked the wiring going to my lights in the trunk area, and I can't find any bare wires that might be shorting out or crossing. I had all my interior trim pieces off a while ago, and the wiring loom seemed in good condition from the dashboard area all the back to the trunk. Does anyone know what might be causing this, or know where I can check around to find a brake light controller circuit board that I can inspect for burns or corrosion? Thanks!

 

In a property working brake light circuit, the brake pedal switch is supposed to be the sole source of power to all brake lights. Any auto on/off headlight circuits in the car are ahead of the brake light switch.

Speculating power is being back feed from the headlights to the brake lights.

Two of the original incandescent brake light bulbs were dual filament that shared a common ground. The bulb shared a brake light and tail light filament in one bulb. If a problem here it would be possible for power to go from the tail lights to brake lights.

Did you replace these bulbs with LED and if so how did you do this?

There is a brake light out sensor after the brake pedal switch. The sensor is connected to the gauge fuse. Might? be possible for the sensor to fail and feed power from the gauge to the brake lights.

The sensor is on the drivers side of the trunk wall.

Make sure the brake light switch is working.

With brake switch off and tail lights on, check the wiring at the brake light bulbs to determine if the headlight power is coming from the sensor side or the bulb side.

Check the dual light brake bulbs (LED) for issues.

If the brake lights are on when they should be off, remove the gauge fuse which is connected to the tail light sensor and determine if this turns the lights off.