Check the connection at the back of the foot pedal - might be corroded or broken
try brake switch under pedal
you need to repair the lights and they will both work and your taillights will work properly
check your fuse and your brake light switch on your brake pedal lever.
The tailights might be burned out. Typically the tailights and brake lights are separate bulbs.
The brake light switch may be bad or out of adjustment. The switch is located just above the brake pedal.
the circuit boards on the taillights are bad.
If you are referring to the brake lights it is probably a bad brake light switch. Your vehicle may also have daytime running lights which would be on without the parking lights.
Check your fuses both inside the cab and under the hood
WHAT ARE YOU DUMB REPALCE YOUR LIGHT BULBS STUPID! Not stupid replaced circuit boards checked fuses ran test light . When headlights are on no brake light or taillights and have all new bulbs stupid. Turn headlights off brake lights work, so figure that out smart man
in dash lights
Check your fuses! -I once got a ticket for 'no taillights' when my dashlights were fine -it was the fuse.
Check bulbs or stop light switch most likely located at top of brake pedal under dash area Check the fuse and inspect the taillights for a good ground. Check the harness connectors also.