As groundscr8per stated, but with the pin positions at the amp.
2003-2006.
Subwoofer outputs at the amp (smaller plug):
For Escalade/Denali/LUX/Y91 option:
Left (+) Dark Blue/White "E"
Left (-) Light Green/Black "D"
Right (+) Dark Green "B"
Right (-) Light Blue/Black "G"
For Tahoe/Yukon/Non-LUX:
Left (+) Dark Blue/White "B"
Left (-) Light Green/Black "G"
Right (+) Dark Green "C"
Right (-) Light Blue/Black "F"
You can meter the wires (voltmeter set on continuity) for the wires at the connector underneath the cupholders. But if you remove your center "glove box", your amp is exposed and you have much more room to work with. Not sure about the Escalades, but on a Tahoe, its 6 phillip screws and (4) 7mm bolts at the bottom of the glovebox.