Warning: maybe stupid question ahead lol

I have the raxiom vent gauge installed and a rear diff cover which has a threaded port (1/8npt) for a temp gauge, so why not add the sensor and utilize one of the two 0-5v analog inputs for the raxiom? My question is, where does the voltage input come from for such a sensor? The raxiom gauge has two inputs for such applications, but doesn't have an output, so am I supposed to just tap 5v somewhere and run it through the sensor and back to the gauge as though the sensor is just a big resistor? Where do I find 5v in a 2018? Or do such sensors take standard 12v and drop it all the way to a max of 5v back out?

If anyone's done this before, I'd love a recommended 0-5v output, 1/8NPT temp sensor and a specific wire or fuse I can tap to provide the signal. TIA

 

Appears it uses the obd2 port to talk to the computer. Power would apparently come from that connection. Just a guess.

 

5 volt supply from the PCM to the 3 wire sensors for Analogue operation. 5 V, Ground return, and Signal lead.
The Signal is converted to digital in the PCM because it's a computer and is digital in program operation for Digital display or other uses.
What you need is an independent Analogue Gauge and Matching Sensor and supply switched 12 volts to the circuit.
What really practical purpose is knowing the rear Temp. besides just wanting to have it?
Good luck.