@jimmyjall , Jim, You are certainly not the only one with this issue, just try a search and you will see. Quite a few forums suggest bad connection at the battery( could not hurt, to remove battery cables and clean connections), I believe this probably does a sort of reset to computer ECM/BCM also. Some of the auto parts suppliers offer free code reading like Pepboys, Nappa, Advanced auto parts,etc and some of the guys are very knowledgeable and may have seen the issue often and put you on the right track. Not positive if there scan tool can retrieve all codes like from BCM, but they will normally let you know if this is the case.
Below is a write up of what MSHax from Hummer Forums found, Link at the bottom.
Armed with schematics, I dove into the lighting issue today. Found something very interesting. I tested and probed just about everything imaginable; no shorts, no breaks, all good clean lines with low/no resistance. You'd thing think that a former BMW/ASE master technician with a degree in automotive engineering would have less trouble with this, but it just goes to show that sometimes we're TOO MUCH of a technician. While tracing lines I found that the connector on back of the fuse box that the fuse plugs into wasn't making contact. The sheathing was fine but for some reason the wire pulled from the connector. Looked great, but had a gap enough to create an open circuit. I grew up in Detroit, so I'm conditioned to love GM, but sometimes they scare me. What ever happen to "instrument panel" in the labeling? I mean I get it, there is more than just the dash lights on that circuit, but there wasn't even anything in the manual saying TBC 2B was instrument panel. Oops, probably shouldn't give out the secret, now there will be less people getting dealer work for dash light. On that note, if I disappear and don't log in for a while it's because GM bumped me off for giving out information that the dash panel lights are connected to the TBC 2B fuse and the wiring behind the fuse panel can become faulty.
Good luck. I hope this helped you out, if so let me know by pressing the helpful button.