Tail lights work but brake lights don't - New Yorker Chrysler Cars & Trucks

Simple test: access the brake bulb, keep the brake pedal pressed a little (use a too box or something similar) and measure the voltage between the central connector on the bulb and the bare metal of the body of the truck - if you get 12 volts then there is a defect in the wiring inside the rear lights, if you don't get 12 volts then either the switch that commands them (on the brake pedal) is faulty or the wiring that connects them to the rear bulbs has a break in it.
Do another simple test: take the brake pedal switch apart and join the 2 contact wires in there: if the lights light up then the switch is faulty, if they still don't then the wiring is faulty. If it's the latter you will gonna have a lot of work to find out where the break is - in the worst case scenario it will be under the carpet so the entire interior of the truck will have to be taken out to access it. it will be a very big job, better left to a repair shop.