Ok here's the schematic. Please reply if anyone has questions. I tried to note the approximate lengths I made for each section of the harness... I thought a bit too long is better than too short in this case, but don't accept those lengths as necessarily perfect. My intention is to put the Curt 2-3 adapter inside the vehicle where the jack goes since I'm not sure it's completely waterproof, but if someone else knows otherwise please shout.
All wire is 20ga TXL I bought from wirebarn.com, except the white ground wire which is 16ga from the 5-pin OEM harness split to the DT6 connector. Everything is wrapped in techflex wire loom to resist abrasion and any exposed wire ends as well as the techflex ends either use a bit of heat shrink or some 3M Super88 tape (or both) to protect and secure.
Parts list is above in this thread. In addition to the above parts the diagram below requires the Curt 2-3 adapter (NOT the 3-2 adapter!), 3 sets of DT6 connectors and 2 or 3 sets of DT2 connectors (I only drew 2 but you may want to use a DT2 to allow for easy separation of the "Green - 1" and "Yellow - 3" wires which come off the OEM Y splitter and connect to the DT6. Plus the wire I listed above (I bought a 10 pack of 20' lengths in assorted colors).
Close ups of connectors below as well.
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OEM Y splitter/extension. Note that although I drew it as splices in the schematic, I actually built it as a Y where there are 2 wires in each pin in the connector on the right. I used 3M Super88 tape to wrap the harness as the rubber wire grommets are really only for single wire weatherproofing and with 2 wires coming out of them I was concerned it wouldn't be water tight. Super88 is pretty sticky and holds up well to water, but even still I'll add a zip tie over the ends and likely slip this section inside a split wire loom to help ensure it doesn't unravel.
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The above wire goes to this Curt 2-3 adapter below, which converts the turn+brake light signal from the trailer plug to separate turn signs and brake lights. If you don't use this you'll end up with your turn signals lighting up along with your brake lights unless you tap the brake lights separately off the vehicle housing. The adapter is about $20 and makes this a cleaner installation which does not require any taps (my preference).
I'm planning to mount my Curt 2-3 in the jack compartment, so in the harness below the right side Roadvision wiring is shorter than the left side. If you put your 2-3 adapter somewhere else you should adjust the wire lengths accordingly.
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For the lights themselves I just added DT6 connectors to the ends of the harness. I'm hearing I should probably heat shrink and/or 3M Super88 wrap those round connectors. I could have cut them off and put the DT6 connectors closer to the lights, but I wanted to keep them as factory as possible so if I have issues with these lights in the future I can easily remove/replace and send them back unmolested.
Note the lights only use 5 pins so for pin 6 I added an unused wire and just cut it short and left it unattached. That way the DT6 connector is still waterproof.
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