I'm sure you can get a 12v signal. The problem with PWM systems is it's not stable. I installed a backup camera in my VW and tried to tap power directly. The image was scrambled because of the PWM. But my aftermarket stereo harness (edit: the PAC RP4) provided a stable 12v lead so I was able to use that instead. Be that as it may, I'd personally prefer to follow the instructions rather than poke around the factory wiring
One thing to check: is there a place to plug in the harness itself, if you were able to buy the harness from Tesla? From the photo you posted it looks like an add-on. However it's rare for car manufacturers to not hardwire that stuff in so I'm not optimistic...
Thanks. Very helpful comments. I think we would need somebody with a factory plug to trace where the wires are feeding from. I bet it is tapped somewhere in the rear of the car, rather than an additional wire directly from the battery.
