Further data:
Old trickle charger dead-no output though charge indicator is green
Purchase new trickle charger
Data from vehicle:
fuse keyoff key on* *new trickle charger connected
LCD 13.1v 12.6v
ECM 0v 12.7v
CCM 0v 12.5v
Data matches normal power side of CCM (service manual section 8A-50.8)
Looks like next step is get into the dash to check ground side resistance thru harness to ground. I contacted
http://gmautocomputers.com/ who rebuilds the CCM and ECM's for their experience. I described my symptoms to the gentleman and he indicated it fit a CCM failure, and these units are susceptible to power spikes (16v+). (Avoid jumping vehicle with a battery booster). Possible power spike from old charger that failed took CCM with it since CCM is always powered up. Rebuilt cost $280, current 10 day turn around time. I'm still hoping for a ground side issue (get out of jail free card- though it's feeling more and more like a Hail Mary pass).