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

Module Power, Ground and Serial Data
Object Number: 2064678 Size: FS
Figure 2:

Communication Signals and Controls
Object Number: 2064681 Size: FS