GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2009 🢒 Yukon Denali 🢒 Power and Signal Distribution 🢒 Data Communications 🢒 OnStar Schematics
Figure 1:

Module Power, Ground, and Serial Data
Object Number: 2075489 Size: FS
Figure 2:

Communication Signals and Control
Object Number: 2075492 Size: FS