Here's the reply I got today from PAC technical support. I'll try again this weekend when I have time and let you know how it goes.
The yellow wire needs to be connected to a 12volt source on the factory 24 pin connector, and the black wire needs to be connected to ground. I sent the instructions and a pin diagram for you to look over. The radio will automatically recognize the unit, all you need to do is push the aux/cd button to access the auxiliaries.
Thank you,
Joe Riggs
Tech Support
PAC
1502 S. Santa Fe St.
Santa Ana, CA 92705
www.pac-audio.com
714-835-3022
800-854-3133