Here's the "kicker". As the car was warming up and I was making notes of the raw ADC value and the converted (degrees C) value in eehack and what the ADC value was in the ignition controller, something strange happened. Around 50C the ADC value from the ignition controller jumped from about 188 (about 1.2vdc) to 730 (~3.6vdc).
Follow the data in the "M" (map) field below...
Code:
R4185:A25:D0.44:C6:M187:V796:T1:E0:L0:S0
R4131:A25:D0.44:C5:M184:V797:T2:E0:L0:S0
R4112:A25:D0.44:C7:M185:V794:T3:E0:L0:S0
R4105:A24:D0.44:C2:M184:V795:T4:E0:L0:S0
R4153:A23:D0.43:C1:M185:V798:T1:E0:L0:S0
R4187:A23:D0.42:C8:M188:V807:T2:E0:L0:S0
R4208:A24:D0.42:C4:M189:V811:T3:E0:L0:S0
R4210:A25:D0.43:C3:M732:V810:T4:E0:L0:S0
R4183:A25:D0.44:C6:M734:V812:T1:E0:L0:S0
R4144:A25:D0.44:C5:M733:V811:T2:E0:L0:S0
R4124:A25:D0.44:C7:M731:V809:T3:E0:L0:S0
R4132:A25:D0.44:C2:M731:V809:T4:E0:L0:S0
R4134:A23:D0.44:C1:M731:V813:T1:E0:L0:S0
Immediately an "ut oh" light went on and I started wondering if I'd done something stupid like shorted out my PCM. But after letting it cool down I re-tested from 44C to 52C with a volt meter on the pin, and confirmed that the PCM must be switching between two different voltage divider networks for improved linearity. Pretty neat.