When connecting my 4k tv to my onkyo avr I can not get hd audio. The avr always reads pcm I've tried 2 tvs even tried a brand new avr and same result. It's happening with ps4 and pc. As soon as I hook up my old LCD 1080p tv the audio works fine
What do you mean by "hd audio"?
If you mean lossless audio like Dolby TrueHD those do not pass through TVs unless they have the new forthcoming eARC. Your sources have to be connected directly to the AVR with HDMI.
If you mean surround sound did you set the audio output type of the receiver to bitstream in the TV audio menu?
If you did try turning CEC off in the TV menu.