Here's the latest.
I tried the wonky LM in another install that I know works, in case my friend's supplied harness was wonky as well. My HC did not see it at all, as per the first time using the supplied harness.
I then tried to determine if the LM was 'on'. I checked and I have 16 volts on the track, putting the multimeter to the blue & yellow wires/pins showed 15.55 volts, so, yup, it's 'on'.
I tried to clear the password, but it couldn't find the module, so it was unable to clear any pw.
I'm using my HC, not my friend's. To the best of my knowledge he already has his HC back.
What's the next steps for this wonky LM?