Phil,
I have a 2015 Chevy Silverado 1500 LT. It currently has DL8 mirrors I want to go to DPN towing mirrors. I want to use the gm mirrors part number 23372182 - a kit with both mirrors. If I don't care about the turn signal and courtesy lights on the mirror - just want the manual folding, heated, and remote adjustment for the top mirror, do I need the harness or can I simply replace the mirrors and plug in? According to the GM instructions I dont need the RZY harness. I would order your harness later if all that needs to be replaced is the harness with no additional wiring. The GM instructions have you going into the engine compartment and running additional power wires. Does your harness avoid that, and would your harness activate the turn signals in and on the mirror and cargo/courtesy light? I'd really appreciate your help. Sounds as if you've figured this wiring out entirely.