Looking for input regarding problem w/ a 2004 Envoy XUV (5.3 V8)
Hope OK here in the BowTie brigrade; figured GMC still counts...

My wife went out after work and upon trying to start the car she said it made a weird noise, apparently something like an electrical generator winding down for just about a second - didn't sound like it tried to crank like you normally here when the battery dies.
Also, the key is stuck in the ON position and will not release to OFF for removal - this sounds like a common problem when the battery is dead from brief Google search.

I arrived and hooked up jumper cables; didn't even have lights when the cables were hooked up - used two different sets in case one was bad.

The 40 amp ignition fuse (slot 41 IIRC in engine comp panel) was fine.
The fact that the jumper cables did not even provide lights to the dome has me concerned that it's not a simple bad battery problem.

Thoughts??