I know I'm resurrecting an old thread, but I figured I'd post on the details of the connector and how I tapped into it. It took some research to find the details, so it probably would save people some effort if they want to do it the way I did it. I wanted to keep the Tesla harness unmodified, which meant making a custom harness that gave me the 12V and ground separated. I have a 2016 Model S Pre-facelift, so this is what worked for me.
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The connector is a Male Yazaki Yesc Kaizen Unsealed 2.8mm 4 pole:
7282-6446-40
The female end is
7283-6446-40.
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Also need at least 3 of each of these terminals when using 18AWG wire, assuming you want to pass the 12V though still.
7114-4111-02
7116-4111-02
The Red/White wire is 12V. Ground is the Black wire. I basically made a passthrough harness, then tapped into the 12V and the ground of the passthrough. I used buttsplices since that's what I had on hand. I didn't have their actual crimping tool for the terminals, and had to resort to using two separate manual crimp tools I found that were close enough sizes, one for the wire and one for the insulation grip.
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I'll be honest and admit this is probably overkill and most people are better off just using a positap to get what they need. The connector parts weren't easy to source since nobody uses this particular one anymore in current car production. I actually have some leftover parts, enough to make another 1, maybe 2 if I'm careful.