W-Body Car Audio: GM Factory Wiring Harness

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GM Factory Wiring Colors: 21 Pin Radio Connector

Having seen this question asked more than once at forums, I figure it's time to provide a bit more information on the subject. When you pull out your factory radio, you'll see four plugs on the back. You'll only need to use three:

The black plug will have wires for power, ground, illumination, power antenna, etc. (Pins 5-10)
The white plug will be for the front speakers (Pins 1-4)
The blue plug will be for rear speakers. (Pins 17-20)

The table below is a representation of the different wires and their purpose.

11 L-Aux*	1Left Front (-)
12 Aud-C*	2 Left Front (+)
13 R-Aux*	3 Right Front (-)
14 Aud-C*	4 Right Front (+)
15 Voice*	5 Ground
16 Ground	6 Parking Lights
17 Right Rear (-)	7 Illumination
18 Right Front (+)	8 Power Antenna
19 Left Rear (-)	9 Ignition
20 Left Rear (+)	10 Battery

The background color represents the color of wire going into the harness. The colors are the same at the speakers as well. If your aftermarket radio does not have an illumination option, do yourself a favor and cap the dark gray wire in pin #7 if you cut the harness off.

If you feel uncomfortable cutting off a factory wiring harness, look to the right for links to other articles about installing aftermarket head units in w-body cars.

* I have no idea what these are used for.

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