Power, Ground, Data Communication, and Amp, Radio, Radio/HVAC (U2R, U2S, U2T)
WARNING: This page is about a different car, the 2013 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
Fig 1: Power, Ground, Data Communication, and Amp, Radio, Radio/HVAC Wiring Schematic (U2R, U2S, U2T)