Great... thanks for the help, everybody! (sarcasm) Well, just to keep all 3 people posted, I narrowed the problem down to the IHKR (version III in my auto). Upon removing and disassembling it, there was quite a bit of nasty corrosion on 4 chips and over a number of circuits.
I tried to clean that, but it looked like the damage was too severe. Plugged it back in and, as I suspected, it didn't work. SO I've ordered a used/working unit to swap and hopefully that does the trick.
I'll post results... should anybody wish to read them (or respond).