Need to know where these ground connections are going to

What is the point of all this? The primary ground cable should go from the inverter (DC-DC converter) to body. That's where the highest current will go- inverter is the power source, and almost all heavy 12V loads are grounded to the body (12V battery, fans, defogger, etc). All the other powertrain grounds give some redundancy (and reduce EMF noise?).

Unless you have a bad cable with voltage drop under load, you gain nothing.

Anything that has orange cable is high voltage- leave it alone. could have 2 wires (DC volts for A/C compressor?), or 3 wires for the motors- it's still high voltage.

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It seems like you're starting in the middle of the story. What are you fixing and why would you not fix it as designed since these cars last for decades and hundreds of thousands of miles?

As for the orange cables, amen to @mr_guy_mann. I'm an electronics engineer and former industrial electrician and I would not modify those except under the most dire emergency situations; as in "I gotta get this running or someone will die." Which I can't imagine ever happening.

 

This seems to be part of the same project as your other thread about replacing a bunch of wires with vastly heavier-gauge ones.

As I suggested there at greater length, it could be very advantageous for you to sit for a moment and ballpark out the gains that you expect from those modifications. You can use Ohm's law to do it, and it can be done in a comfy chair with a calculator for a lot less time and money than rewiring the car. It would also widen your options, so you could decide, say, to selectively rewire some things, if your calculations show a cost/benefit for them above a threshold. (I am not predicting they will, but it's up to you to set the threshold.)

In this thread about grounding, there are some more things to think about.

When you look in the car's wiring diagram (more info), you will find the "ground points" section gives you a lot of the information you are asking for here. The rest will be in the actual "system circuits" diagrams.

When you look in the wiring diagrams, you will notice a number of instances like this one, where Toyota did not tie grounds together, and had good reasons they didn't.



While Toyota's usual go-to color for a general ground is white with a black stripe, here (from this post with more details here), you will see a brown wire used as a ground, and Toyota uses a bunch of those under the hood to provide a quiet ground reference for important sensors, protected from the typical electrical noise on the general grounds. This picture also shows another, completely dedicated, white (no stripe) ground wire, also provided with a shield.

Depending on how you "tie them together", you could end up compromising the noise isolation that Toyota designed into the system. It would also be possible to create ground loops, paths joined in more than one place and subject (think Faraday's law) to induced noise thanks to magnetic flux changes through the area inside the loop.

When you look in the diagram at the circuits that are shielded, you will also notice that sometimes the shield may be grounded at both ends, sometimes only at one end, and those decisions (including which end, when it's only one) were also deliberately made by the engineers.

I am getting a sense that you may have a project here where you are going all in on applying a certain few principles of electrical design, in isolation from other principles that also matter, and that by approaching it that way you could end up with some mistakes that the Toyota engineers spent more years learning how to avoid.

I will especially echo jerrymildred and mr_guy_mann where the high-voltage cabling is concerned.

 

Based on his 10,000 watt rms amp thread today, he thinks upgrading the inverter wiring will allow more power to be drawn for his subwoofer hair moving machine.