Wiring diagram

Hello, this is a tough one to find because these old diagrams don't label anything. Have you tried unplugging other sensors that use the 5 v Ref? Most of the time a shorted sensor will pull the 5-volt reference down.
If you keep your multimeter on the ref wire and start unplugging sensors until it returns, that's where I start if I'm missing the 5volts. I will keep looking for the correct diagram in the meantime. So, unplug any sensor that would use it, Map, EGR Position sensor, TPS, etc.
I will update this with diagrams when i come across the right one for you.

Okay. so, it appears the 5-volt reference is this orange/white wire, in the diagram it's not labeled but it's shared with the MAP sensor, EGR valve position sensor, and the Throttle Position Sensor.
The black/white appears to be the ground, the reason I say that is if you look at the second diagram, it's the Temperature sensor, and it cannot share a 5-volt reference and the wire runs directly back to the ECM, and the black/white wire runs out into the Harness and can be shared with other sensors.
Okay, the last diagram confirms the Ref Voltage at Pin 26 going to TPS. So, it is the orange/white wire.

Looks like its Pin 26 at the ECM running out to the sensors.

https://www.2carpros.com/articles/how-to-check-wiring

https://www.2carpros.com/articles/how-to-use-a-voltmeter