I've lost all lighting on the dash except for turn signals and warning lights. Instrument lighting, radio, gear selection and HVAC lighting all went out at once.
I've checked the fuses and they appear good. Bad ground perhaps?

 

Bad Ground, Bad Radio, Bad BCM, Bad Harness. There are several possibilities. Does your Alarm work? Door locks, Dome Lights? Knowing that could help narrow it down!

 

I remember that happened to someone I knew before. Same problem on a trailblazer, in the fuse box under his hood was a 100amp fuse that is different from the others it's screwed down by two screws on opposite terminals, it connected lines heading directly to the battery, it was I think I $30-35 fuse, we did the swap with a new one and lights lit up again. Not sure if our montes have this same fuse but once other tech gurus in this forum read my post I'm sure they'll know what I'm talking about exactly and they can chime in and which fuse is it exactly and how to locate it.

 

it was either a 100 or 115amp fuse I am leaning more toward the 115 for some reason I remember it's amperage struck me as something different from the rest

 

The items that work: dome light, warning lights, DIC, turn and hazard signals, locks, windows, auto-dim on mirror

Items that don't work: Instrument lighting, map lights, radio and HVAC