Headunit not turning ON when engine is running

[Knobz]

Hey. So I've been having a problem all of the sudden with my headunit not turning ON when I start the engine. Funny part is when the key is in accessorie the stereo turns on and works perfectly normal but then as soon as I start the engine again it stops working. I have know idea why it's doing this...

Anyone have any ideas what might be wrong?

 

[YukonXL04]

pull the radio, and check for voltage on the red ACC wire with the truck running. Im wondering if something isnt wrong there.