Hi guys, new to the Tahoe and I have a strange problem. The truck sat for awhile and the battery went flat. I put it on a charger and it would only come up to 11.5 volts. I hooked my jumper box to it to supply extra juice and nothing. I turn the key and nothing comes on. The dash doesn't light up, the radio doesn't come on and it won't crank. Thinking the battery was probably toast because it's out of warranty and won't hold more than 11.5 volts I replaced it. Checked voltage on the new battery and it was 12.5. Tried to fire it up and same thing, nothing. No crank and nothing on the dash comes on. The door locks work and the lights work. I've never run into anything like this before and it came out of the blue. The truck was running fine before the battery died. I'm hoping there's something simple I'm not aware of on this truck like some weird security feature. Thanks for any help!