Patiently waiting for the nest occurance. I might start looking at headlamps switch and wiring anyway. I did find a small chaffed wire on the SIR coil. However replacing it has not fixed the problem.

OK our symptom has returned. When this symptom is present there is a loss of 12V ref on BCM X1-17 and BCM X3-12. I have tested for short to ground-OK. I have disconnected the headlamp switch-no change. And the SIR coil-no change.

What other circuits may be grouped to these inside the BCM that I should look out for?