I'm looking at the female plug schematic. Why are there TWO L/R and TWO U/D?
Yes, actually I was just guessing.
Look at the schematic again, Ken. The female plug lists two R/L circuits with different circuit numbers (540 & 543). Those numbers correlate to the driver & passenger side male connectors. You have a R/L for each mirror ... circuit #540 for one side, and circuit #543 for the other. And no, this time it's not a guess.