Help... Which one is the ground wire on the stock wiring?
 

not the one attached to head unit, but the wiring behind the dash.
Thanks...

What are you attempting? If you just need a ground, find a bolt touching metal and wire a terminal to it. Find an unpainted surface, there are lots of options behind the dash.

Thanks... I actually found the wiring diagram. Ground is the black/blue wire. I did have the ground (from head unit) attached to metal behind dash, but the HD channel was not coming in good. Now I attached the head unit ground to the car's wiring harness (black/blue) and HD comes on and stays on.