Need Help! My 07 Yukon XL is very very dead

2007 Yukon XL 1500 is dead!

Won't start (won't crank)
The "accessory" key position doesn't turn anything on
The "run" position turns the HVAC and radio on, as well as idiot lights and dash text readouts, but that's about it (The actual gages don't move - I know it has a full tank of gas, but the fuel gage sits on empty).
No shifter position on dash. I can shift out of park without my foot on the brake.
No power locks or windows.
No rear hatch power (I can't open the tailgate).
No interior lights.
No gages.
No 4 way flashers.
If I turn the headlight switch to "ON', the headlights come on, but no dash illumination.
Idiot lights seem normal-ish (I honestly don't watch them close enough when I start the car to know what normally comes on). I don't see anything telling me that it is in an anti-theft mode.
The little car with a padlock on it turns on for a bit, but then it shuts off.

I haven't tried every little thing, but here are a few things that work:
Radio does work
HVAC does work
Homelink does work.
Power mirrors work.

This all stared on Thursday when I wanted to drive the Yukon to my Dad's house. It seemed "dead' when I tried to start it. I proceeded to get out jump packs, chargers etc. The thing wouldn't even attempt to start. I do recall that I was surprised the volt meter never moved when I turned the key on.

Maybe I created a problem by all the jump starting attempts, key on-off, etc. Burned out a computer somewhere? Put it into anti-theft mode? However, I am starting to think that something went wrong that made me think it had a dead battery, but it was really something else.

I have looked everywhere for any signs of harness issues (animal chewing?), and I haven't found anything suspicious. I have checked all the fuses I can find.

Battery cables are in good shape, ground cables seem good. I will loosen an retighten all the grounds I can find tomorrow.

PLEASE PLEASE help!

You need to check the condition of your battery and make sure there are no blown relays or fuses. A weak battery can fool testers and wreak havoc on these computer driven trucks.

Do you have access to an advanced scan tool like the Tech2? If the first two don't lead to clues the scan tool is needed to see what's going on inside the various modules.

swathdiver said:

You need to check the condition of your battery and make sure there are no blown relays or fuses. A weak battery can fool testers and wreak havoc on these computer driven trucks.

Do you have access to an advanced scan tool like the Tech2? If the first two don't lead to clues the scan tool is needed to see what's going on inside the various modules.

Click to expand...

Thank you. With headlights on, I'm holding 12.4 volts. Seems ok to me. I went to 3 local stores yesterday morning looking for a battery, and they were all out. At that point I pulled a battery from one of my other cars and stuck it in there.

No, I don't have access to a Tech2. I assume I would need the genuine GM version, and not the $300 amazon or ebay version.

Pull the battery cables, clean up everything and try again, the cables are known to go bad (corrode inside)

That battery seems low to me. The codes won't set until it drops to 11. Check the grounds too.

The Ebay and Amazon ones work just fine; it's what most of us on here use. The BCM wants to see 12.6 to 15 volts. That's the computer that all this stuff originates from. I keep flipping the pages so to speak and if that is your battery voltage, it's too low. If more than a couple years old, you can try putting it on a trickle charger but I reckon it's time for a new one.

They are a Group 48 battery, not real common except amongst themselves (GMT900s).

I have a new battery in it now, and it acts the same way.

I didn't map out every fuse, but roughly half of the fuse box has power and half does not. Perhaps the BCM is supposed to turn on the ones that don't have power. It seems really odd to me that the 4 way flashers don't even work.

Addicted said:

I have a new battery in it now, and it acts the same way.

I didn't map out every fuse, but roughly half of the fuse box has power and half does not. Perhaps the BCM is supposed to turn on the ones that don't have power. It seems really odd to me that the 4 way flashers don't even work.

Click to expand...

Hmm. So something is preventing power from getting to half the fuse box? @gpracer1

swathdiver said:

Hmm. So something is preventing power from getting to half the fuse box? @gpracer1

Click to expand...

It seems so. I'll dig more tomorrow. It is hot as blazes today, and a big thunderstorm just started. Of course, my 5 garage bays are all full of other stuff, so I am working outside. First world problems, right?

I'm going to order a Tech2 or something similar tonight. Any recommendations?
I don't want something that won't work. Looking at this one. http://a.co/0zeAwea

@Rocket Man

Hey Mark, is that guy you bought your Tech2 from still selling them?

Mike, I'm not familiar with the Autel. If you had to replace your BCM for example, the Tech2 can be used to go online and get the software to reprogram your module(s). If you decide on a Tech2, whichever the vendor, make sure it has the latest PCMCIA card with 33.004 software. Mine came from China and DHL delivered it lickety split, like 3 or 4 days.

You could try pulling the upper fuse box off also and clean up the contacts, it's either that or the battery cables, just grab the handles and pull up