check the brake light switch behind the brake pedal under the dash.
Check the Brake switch that's mounted on the brake pedal bracket, they can get jamed and cause the contacts to pass the 12 volts to the lights. Good luck!
Short in the wiring or inside one of the plugs.
you might have a bad Flasher relay.
More than likely the flasher relay is defective. Replace it.
fuse, bulbs
brake light switch would be most common cause
the abs modulator has a proportioning valve inside for normal braking.its an internal leak
BAD BRAKE LIGHT SWITCH AT TOP OF BRAKE PEDAL
The BOO (Brake On/Off) Switch may need to be replaced. If it is bad, it would cause the brake lights to NOT illuminate when the brake pedal is applied.
Possible ground issue at the taillights.
it is a defective speed sensor.
Blown fuse or defective brake light switch.