wiring for trailer 05 chevy

I have a friend that has a 2005 Chevy pickup, he is wanting to hard wire trailer plug into vehicle wiring. We put test light on back of trucks wiring and found all the wires but what I am wondering did Chevrolet change the brake light system from turn signal and brakes in same circuit to separate circuit for each?
We wired trailer up and all light work on trailer except brake lights. I tested plug and it doesn't show brake light either. Have I possibly wired something wrong or do I have to have converter to run brake lights on this vehicle.

In those year trucks, there is a separate fuse for each trailer function. Check the engine compartment fuse box...