For the coolant temperature sender you should measure the resistance between the two pins

I am not so sure about that, the wiring diagram does not cross streams between these, one is gauge, one is dummy light. 99% sure it is pin to base.

I have a ST, and when this gauge madness FIRST started on the drive to South Dakota for the 928 meet a few years back.. in the high desert at 110+ degrees and AC on, the ST in the car was logging 220-222 degrees between both NTC-II outputs.. but the light on the gauge was coming on well before that.

That light should not be on below 244 degrees.. that much is documented.

But I did find a cross reference to VDO for this sensor, and I have attached it's data sheet.. and my sensor is...working perfectly! (VDO 323803001020D)
Temperature range: +40 °C to +120 °C
Thread: M14 x 1.5
Sender resistance range: 287.4 - 22.7 Ohm <--Fat pin 6.3mm
Sensor signal: 1-pole common ground
Warning contact: 115 °C ± 3 °C. <--Small pin 4.8mm

Technical/Tips/VDO temperatuur-sensors-2-1.pdf

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Sending Unit for Water Temperature Gauge 928 606 201 01

The coolant temp sensor at the water bridge of a 928S4 GT and GTS is a two terminal dual function sensor.
One is for the light, one is for the gauge.
A 'quick and dirty' check is to ground out each wire. One will light the light up, the other will peg the gauge at full hot
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Easy just connect them and drive the car if your temp gauge does not move at all, swap them around and you should be fine.
You can also check the resistance before installing. One plug will show resistance of some sort the other one nothing (always measure against the housing of the sensor).
Blue/green is the "idiot light, blue/yellow the temperature gauge. If you look very closely at the sensor, you might see nearby one of the pins a "W" for (Warnung, German for Warning) and a "G" (Geber, German for sensor).
Schocki