So, I just converted from my stock non-RF single CD head unit to a MMCS touchscreen/nav unit. Everything went together plug and play, except one thing... My RCA inputs no longer work. They're still connected, but there is no option to use them as a source in the Mode menu. Any ideas on how to get them going again? TIA

 

Are they for video input? A lot of radios have a handbrake cut-off where video will only play if the handbrake is engaged. There are ways of getting around that. Sometimes grounding the wire. Sometimes using a relay.

So on my Pioneer AVH-4200NEX, bluetooth was grayed out in settings because that wire wasn't connected.

 

No, they're just the red/white audio RCA ports.

 

Solved!

 

how?

 

The harness was missing a system ground that tells the head unit that it has aux capability. I pinned that in, ran it to the dash frame, and the aux option showed up on my menu