Sunday morning, my battery was dead. I have one of those fancy battery chargers that can tell the percent of charge it is holding. So I tried to charge it, it bounced up and down between 10% and 25%.
I bought a new battery thinking, 8 year old battery is done with.
I popped in new battery and everything was good.
I went for a ride and something funny happened - all of my dashboard gauges went down but speedometer stayed on. My radio say "XM ERROR".
So I did a u-turn to head back home as this was still running. A few minutues later, all th3 gauges came back on and worked normally. I get home and power off h2. It started back up. I did it a few times. I thought it was "one of those things"
This morning, I went to jump in it and noticed my remote keylock didnt open door. So I manually unlocked it and the interior lights did not turn on. I try to start up h2, it turns over but doesnt start.
The passlock light does come on for a second and goes off when I turn it one (like a normal power up self test).

Any ideas what to check?

 

Ok
I decided to call a Mobile Mechanic. (Dan The Man)
I explained to him what I wrote above and took pictures on my phone of the battery terminals, and lights on the dash and stuff.
First he said "try another key" - possible passlock issue - no change
He said "unplug negative terminal for about 10 minutes or so and reconnect it"
I did this but had to call someone so it was disconnected for about 30 minutes.
Low and behold - the truck came back to life

So he says "drive it around local for a few days and see if the problem occurs again. It could be that I changed the battery fast enough ecm/bcm didnt discharge and may have been in a strange state.". Which sounds plausible as I swapped batteries in less than 3 minutes.

He says "The electronics on these types of vehicles can act almost possessed"

Anyways I will report result as time progresses

*maybe this will help someone


---===EDIT===---
This guy could have soaked me but was honest. I am not a super-duper car guru like a lot of the members here are so this was cool to me

 

This issue also happens to Suburbans and Tahoes. Replacing the battery can cause strange electrical problems. My dads 05 Sub messed up the CC after unplugging the battery. I finally got it reset but it's really strange.

 

Well the issue still persist.
Grrr

I think I am dealership bound

 

Did you get it solved

 

Almost -it is at dealer.
They said "you got an aftermarket security system installed in here that shorted out and is causing the issues"
So... $800 to remove it
(this includes a detailing, fuel injector replacement (said they were pretty dirty), and flushing the differential (which I do remember when I bought the truck and wanted the fluids changed - they said they couldnt do the diff at that time)
Said everything else looked ok

I figured they would find something to UP the price. I dont care, mentally I envisioned a $5000 issue with all electronics needing to be replaced.
*Hope for the best - plan for the worst

I know, I know.... the mechanics in this forum are thinking "if he does it himself, he can save $775"
I like the peace of mind from a dealership giving the truck a 23 point inspection and fixing 2 issues

 

Hopefully mine is at the same . I do also have an aftermarket alarm (cliford)
I was installing a led lights and made a mistake connecting the power to the Drl . I assume the install of the led cause the issue maybe it mess with the alarm
I will post after the dealer gave me an answer
Thanks

 

Good luck. Update with results