No electrical power to anything, battery is good

[Bono]

Full disclosure, this is on a 2021 Yukon.  I have a 2021 Sierra Denali sitting right next to it and have been swapping various things to troubleshoot with limited (really none) success so far.

 

I bought this as a flood car and expected to have issues.  It looks very clean on the inside but is essentially dead electronically everywhere.  So far I replaced the junction box inside of the cab and have swapped the main fuse panel with the one off of the Sierra and have the same results. When I hook up the negative cable, I am getting some sounds out of the driver side firewall.  I found a Spireon GPS tracker plugged into the OBD port and after removing it, I also get a couple of cycles of a small pump sound under the vehicle.

 

I understand things like the seat, HVAC, radio, instrument cluster, etc may all be bad but I would be surprised if everything actually was.  I have good power to everything from the battery to the power distribution on the positive side of the battery and have even replaced that with no change.  I have good power to the main fuse box verified at the post.  I've also swapped the entire fuse box with the Sierra along with the ECM and TCM (I know if won't actually work but worth a shot).

 

The reason I think there is something obvious vs every single thing being bad, is that when I push the parking brake button, I can hear something under the vehicle (transmission area).  I also have a small orange light in the button where you can turn the park assist on or off.

 

I know the obvious answers are short to ground, bad ground, bad battery, etc.  I've been chasing and searching for the culprit with no avail so far.  Just curious what you think it might be and if anyone has experienced this.

 

Again, this was a flooded vehicle and is a Yukon.  I know how much more traffic this section gets and with my 2021 Sierra Denali sitting right next to it, I have verified they are essentially identical.

[Paul Beaudet]

Sounds like the network isn't waking up.

 

You likely have multiple modules that are dead. Most of the modules inside are not watertight. Anything from the body control module to the radio can kill the network and bring everything to a stop.

 

Here's a video about a similar issue showing one module taking out the network and there a lot less modules in that era of Yukon than today's.

 

I wish you luck.

 

 

 

 

 

[Bono]

I should add, it will also pull the battery down slowly. I can watch it long enough to see it drop .1 volts every couple of minutes. So it seems like something is drawing constant power.

 

While I expected some of the seats wouldn’t work, etc I’m surprised nothing has power, not even the headliner lights.

 

I will start trying to make a list of every module I can find and try to isolate them one at a time. Hopefully someone can point towards one of them being the culprit.

[silveradosid]

you need a decent scan tool to see if you can communicate with any of the modules in the truck. one test to try is measure the resistance on pin 6 and 14 on the diagnostic plug, should be about 60 ohms

[Bono]

I’ll check those and I have a couple of scan tools but nothing I need. I have a Zurich from HF but am trying to figure out which Tech 2 type scanner I should buy.