Check bulbs (double filamented small is for brake lights-large for tailight) Check fuse for stoplight Check stoplight switch
Look for a fuse labeled TAIL LIGHTS. There are 2 separate circuits, one for brake turn and flasher and the other is for tail lights.
It could be a blown fuse. Tail lights and brake/turn are on separate fuses. Apparently there is not a ground problem since brake/turn works OK.
If your brake lights and tail lights aren't working while the turn signals function normally, the issue could be due to a blown fuse, a faulty brake light switch, or a bad connection in the wiring. The turn signals operate on a different circuit than the brake and tail lights, which is why they still work. Check the fuse box for any blown fuses, and inspect the brake light switch located at the brake pedal for proper function. Additionally, examine the wiring and connections for any signs of damage or corrosion.
On a toyota tacoma 2003 SR5 when the tail lights are turned on the brake lights come on and when the tail lights are of the brake lights work just fine what could be the problem. If the truck has a trailer plug, inspect the plug and plug wiring for damage and corrosion.
Are you saying your tail lights themselves do not work and only the brake lights work. If that is the case, check the fuse, and then check the tail light bulbs.
its on different bulbs
Check your fuses.
on some cars the tail lights and brake lights are totally different bulbs gain access to the bulbs and have someone push the brakes so that you can determine which bulbs are the brake lights and replace the tail lights
Check the brake switch at the pedal.
Brake lights should NOT be effected by the headlights. Brake light function is completely independent of the headlights. Assuming you are not refering to the tail lights, or marker lights, which are supposed to come when the head lights are turned on. Not having brake lights when the head lights are on is a big safety problem and should be corrected.
Those tail lights could be the brake lights you are seeing and that would be a faulty brake light switch or the brake light switch is out of adjustment.
Take a hammer to the tail lights then they will shut off but you might have to get them replaced or somting The tail lights you see may actually be the brake lights stuck on because of a faulty or out of adjustment brake light switch.