Check bulbs they are double filamneted smaller for stop lights larger for tailights Check fuse (parking/tailights/dash)
Maybe a bad headlight switch
Brake lights and turn signals are on a separate circuit from the tail lights. Tail lights are on the same circuit with the dashboard lights. If the dashboard lights aren't working either, check the fuse. If they ARE working, check the headlight switch.
Tail markers and stop lights must be red. Turn signals can be red or amber.
Most likely a fuse or a bad ground.
Check the fuses first then check the bulbs.
Fuse, wiring, bulbs
It is most likely the tail fuse. The dash and tail lights are usually on the same circuit
Its the steering colum
if turn signals are working , and brake lights not working, i would replace the stop light switch on the brake pedal
generally the tail light fuse is the same fuse as the turn signals
Blown fuse or bad headlight switch
I would first check the grounding between the truck and the trailer. If the ground is good then bulbs would be the next thing to check.
There is a short somewhere in the wiring.