Strange Intake Air Temp Problem

[W-Car3.1 LH0]

Hello All I have a 1994 Lumina 3.1 LH0 engine. Using TunerPro RT to monitor parameters under the hood. Well, everything is working perfectly except the IAT Temp. I've ruled out the sensor by testing it and measuing the resistance values against the chart in the factory service manual. But I've even replaced it for good measure with OE AC Delco equipment. So I have a 5 Volt reference signal but the sensor is inverted--it's reading low when the underhood temp is high and high when underhood temp is low. It's totally inverted. And when I jump the wiring harness with a paper clip, the IAT reads -40 F. When I unplug it, it reads like 300 degrees. This is eactly opposite from what the Factory Service Manual says it should be. No codes or faults either. Any ideas? Faulty PCM maybe? I thouhgt it might be inverted wiring somewhere but I've found nothing to indicate that and ALL other sensors are acting normally. 24.6 MPG on last fill up. New car sticker says 19 City/29 Highway. If it is a faulty PCM, how does the logic get inverted? So strange to me. Thanks in advance for any advice you may have or give.

[robertisaar]

i think your ADS/ADX is wrong...

with the 5V portion of circuit directly connected to ground, that should register as 0 A/D counts, should come up as roughly 298.85*F. with the circuit open, that should be 255 A/D counts, should see near -40*F.