2005 Chevy Suburban won't start when cold; weird electrical issues

I have an '05 Suburban with starting issues. When it’s cold out (below 40 degrees) and you turn the key, all accessories come on but truck will not crank. It then seems like the power just cuts off…dash lights go out but gauges are fixed in place and a couple of seconds later, I hear a strange buzzing noise from the dash area behind the radio and the gauges will then go to power off position. Then if I try to start it, there is nothing, no lights on dash, no starter engaging, no clicking of the relays, nothing. I tried, on a hunch to disconnect the ground lead from the battery. Had it off for 10 minutes or so, put the cable back on, tightened it down (wasn’t loose to begin with) and it started right up first try in 20 degree weather. I had previously had the battery and alt checked and both were good. Anybody have any ideas?

Just because the cable wasn’t loose doesn’t mean that the connection was good. Removing it and replacing it may have been enough to re establish contact, but if you didn’t clean it good, it may not last.

@Gracie813 how old is that battery. Personally, I hate those side terminal batteries.

Are the “studs” in good, clean condition?

I had almost this exact same thing happen w/my Corolla last winter. I pulled into the gas station, filled up, and when I tried to start the car, it wouldn’t crank, and each time I attempted to crank by turning the key to “start”, all the dash board lights gradually went dim, with some similar as described buzzing noises coming from somewhere. It was raining cats and dogs and was quite cold, so this was no good. But I quickly popped the hood, and discovered that the positive battery connector could be turned by hand. It had come loose somehow. I was able to twist it enough to get the car to start, then the next day when it stopped raining I removed both battery connectors and cleaned them off, then retightened, and never had a repeat. Hopefully this is the sol’n for the OP’er.