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I am replacing the stock stereo in my 2015 Nissan Leaf S. In the center console is a USB port which was connected to the head unit. I'd like that port to continue to work with my new stereo. The schematics for the existing unit has the following:

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The bottom line represents the back of the stereo. Here is the legend for those numbers where the letter under the number represents color of the wire (I don't know what shield means)

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The new stereo doesn't have a schematic because the USB port is built into cable that plugs into the unit. It has 4 wires, black, green, white, and red (ignore the yellow, it's for a mic). Here it is:

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My first guess is that I would ignore 57 and connect 53 to red, 54 to black, 55 to white, and 56 to green. Is that right? If not what do I do and in either case what is the signal shield?

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The signal "shield" should be a foil or metal mesh wrapper around the four signal wires. It is there to prevent interference from the environment, which could make the link less reliable. If there is no connection for it on the new head unit, you're probably best off connecting it to the metal case of the head unit instead. You could also try connecting it to USB GND at the stereo end.

As for wiring the other wires: red, green, white and black are the standard colours for USB, in which case the assignments given in your last paragraph make sense.

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  • \$\begingroup\$ The colors may be nominally standard, but there is absolutely no guarantee that a given device will use them in the standard way. I've cut up USB cables to find black VBus and red ground... It's far better to conduct measurements to identify the power; interchanging the two signal lines is a non-destructive mistake, only leading to failed enumeration. \$\endgroup\$ – Chris Stratton Nov 6 '18 at 4:27

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