GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2009 🢒 Yukon XL - 2WD 🢒 Power and Signal Distribution 🢒 Wiring Systems and Power Management 🢒 Upfitter Provision Schematics
Figure 1:

Roof Beacon - TRW/5G4
Object Number: 2075732 Size: FS
Figure 2:

Police Power - 5W4 or PPV
Object Number: 2187444 Size: FS