2006 2500HD 6.0 Electrical Issues

[tullybrewing]

I just lost functionality of most electrical components on my 2006 HD.  Was driving down the road and my temp, fuel, oil pressure and alternator gauges all dropped to zero.  Battery light came on, airbag light came on, shift indicator disappeared, radio is out, keyless entry and door locks non-functional, no 4-wheel drive, power windows inop, no dome light, no backup lights.

What I do have still working is it starts/runs/drives.  Alternator is charging (checked with voltmeter), tach and speedo work, blower fan works.

I spent >14 hours this weekend checking every fuse, grounds and connections with no success.   I was into the ignition switch and everything south of the steering column and am scratching my head.  The only common item I've come across is my switched (acc) power.  I checked acc power at both the OBDII and the radio to find that this line is carrying half a volt in the OFF position and ~1.6v in the ON position.  I cannot power on a scan tool to check codes.  In checking both fuse panels, I'm reading ~11.8v on every fuse, so I suspect my issue is in the dash.  The battery had a full charge on it when I put it back together and going out this morning, the engine wouldn't crank (low on juice).

Does anyone have any suggestions on what to look for?  Where to look for battery draw?  Why my acc/run position is only putting out a fraction of 12v.  Maybe a bad BCM - does it control switched power when the vehicle isn't running?

Totally stumped and need some help before I throw in the towel and take it to a dealer $$$.