I had to hook mine up directly to the back of radio. There was a diagram of the radio wiring in my paperwork. My dealer purchased my tv aftermarket and installed and later advised I needed to hook up directly for surround.
2013 Salem 30KQBSS TT
Equalizer 4pt Hitch system-12K
2016 Ram 1500 Crew Cab Sport 5.7 Hemi w/8 Speed
I had to do the connection behind the radio also.
Pulled the radio, connected a RCA left and right to 3.5 headphone jack cable, ran that up through the hole in the swivel for the tv mount , when I want tv sound ... Plug into the tv and hit aux on the radio.