Just a followup to my post...
Today, on my third "trip" since I found the problem with the ECT sensor circuit, I noticed that my MIL was no longer illuminated.This looks like a pretty good indication that the ECT sensor problem did indeed cause the PCM to set a code, which should now be stored in history for 30 trips, if I'm not mistaken. If I get a working scan tool, I'll check for it.
I've also been watching the temperature gauge, and it has stayed between one-quarter and just less than one-half scale, which sounds normal.
When my PCM is happy, I'm happy !