Try changing light bulbs check fuses, test light switch, look for broken wires or loose wires.
If it is still on when your car is off it may be a sensor to your brake lights that may need looked at. If it is on when your car is running it may just be something to do with day time running lights. If it is still on when your car is off it may be a sensor to your brake lights that may need looked at. If it is on when your car is running it may just be something to do with day time running lights.
Defective brake light switch.
There should be a switch on top of your steering column that turns on/off the "Parking Lights". Check to see if that is your problem. The switch should show red on the front of it if the lights are on.
check that you have double filament bulbs in tail lights
Check the fuses, check the brake light switch, check the bulbs.
check wire continuity- no power no lights
There is a relay in the emergency brake which turns them off. Sometimes it can be sticky. pull up on emerg pedal.
Take a light tester and check the pins at the truck side trailer plug. With the truck set for running lights check for power at the pins. If there is power then there is a loose or bad wire on the trailer side. If there is no power then there is a power problem on the truck side.
You may need to check your brake light switch. It is a small switch located on top of your brake peddle (up on the arm of the peddle). This switch allows the brake lights to come on whenever you push the peddle.
Behind steering wheel is a set of contacts that disable the brake lights when a turn signal is on, they may be stuck in the off brake light position. Try pushing the turnsignal arm to its limit and then wiggle it....careful you do not brake it off. Also check for brake light switch adjustment.
It's the brake switch. It tells your break lights to come on.
Open bleeder on each wheel and see if it releases. Probably a bad rubber hose at wheel