Good afternoon I’m having an issue with the rear lights on my pickup when the lights are on in the truck, I hit my brakes and the third brake light lights up, and the two rear tail lights will turn off. Also, when I turn the turn signals on, it doesn’t matter which way both rear tail lights blink.

 

Welcome to Chevy. Please lilst yhour vehicle details
Sounds like a ground issue to me or possibly problem in the multi-switch that runs all the lights.
With light off do the brake lights &/or turn signals function properly?

 

It’s a 2001 2500hd 2wd
with the truck and the lights off the brake lights work properly but neither of the turn signals work

with the motor running tail lights stay on either way I flip the turn signal lever it flashes both lamps and if I hit the brake the third light above the cab comes on but both tail lights go off

 

Welcome from Florida. Along with checking the multi switch, I would also check the wiring at both taillights. Look for corrosion, loose wiring and make sure all bulbs are good and making good connection.