The battery ,which gives power to the truck, looses its power because the lights use power from the battery to work. It's just like a batery for a toy.
Corroded, loose, or defective battery cables.
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.
a loose transmission or shifter rod might move the gears around a bit and make it stall
Dead battery or dirty/loose battery connections.
Blown bulb - or loose wire !
If the car/truck is running, it will not make a difference. However, if there was an electrical short on one of the wires that leads back to the brake lights, it might slowly draw power while the engine is off.
check and clean the battery terminals
Check for: 1) dead battery 2) loose or corroded battery cables
Usually problems like that are contributed by a loose ground wire in the system.Check all ground terminations for loose wires or paint under them.
THESE ARE AFTER MARKET LIGHTS FOR MY HUSBANDS WORK TRUCK
Check fuses (if stop lights are not working shift interlock will not release) Check fuse box for corrosion or loose fuses
Truck lights can be purchased from most automotive stores. There are several different automotive stores available and it is likely that they will have lights for trucks.