wiring schematic for stereo speakers 09 avalanche

[09avalanche]

Just wondered if anyone knows much about the wire routing from the radio and the best way to access the radio to get at the speaker wires, since my rear door speakers are inoperable.

I have a sneaking suspicion that when the dealer did recall work for passenger side IP air bag replacement " Takata screwup " they may have done something while in the top of my dash, seems quite possible doesn't it?