Ah, I was reading the harness, which is where I thought you had meant. I’ll check again in the eveningNo reading probing pin 1-2??? There must be something, either 0 ohms or open-circuit; which is it? Where are you reading that ~20 ohms. When you probe 1-2, you are probing the pins of the sensor itself, harness disconnected, correct?
I am disagreeing with above post. Resistance readings on the IAT sensor are quite easy, meaningful, and accurate if it is a simple thermistor; which think it is.