poltergeist in the electrical system

[JimDrew]

Man, that's a lot of places for failures!

 

[intheburbs]

2012 Yukon XL. Stopped for gas near the Canadian NY border. After filling.... absolutely dead no electricaL power. Was able to start. However when getting back on the highway the door locks fluttered rapidly up and down and the dash lit up and gauges fluttered. The tach revered up with no power. I was able to limp along at 20mph on the shoulder. Eventually was able to reach 50 mph. Yes I thought it was a grounding issue. In Canada I redid/cleaned all the grounds I could find. The worst location was the one going from the negative post to area under the front bumper cover. Not sure of the one behind the driver side A pillar ? All appeared good, but the neighbors code reader said misfire # 2. Redid all the coils,plugs, wires last year. Had some spares so was able to get back to Maryland. ??? Was driving on misfire damaging other plug,coils causing the system to go into a limp mode ?
Should note I was pulling a 12' trailer containing a full 12 drawer snap on box. I know. I should have opted for the 6.0 motor. Thinking about the new 6cyl diesel.
Maybe buy a lotto ticket.

Going back to OP's issue - he checked grounds, but did he check for loose battery cables?

 

[Dennismenace]

Ok, so I have been meaning to make a post about this same issue I had - where the dash board goes crazy, door locks will lock/unlock, Tahoe dies, etc. I figured out the problem, and I took lots of video. I will get around to making an official post about this. After talking with my local dealer I learned that these problems are almost always CAN BUS related - a short either in the high speed or low speed CAN BUS's that the GM vehicles have.

Finding a short can be rather difficult. There are some known places that shorts occurs - the frame rail on the bottom/driver's side is very common. Check that harness that runs under the frame right below the driver door. I was told that there have been cases where a harness around the fuel tank is pinched between brackets and the frame rails.

I happen to find one that the dealer had not seen before, and it was quite a surprise. I just so happened to notice that when I parked my Tahoe on a slight hill in front of the Domino's Pizza place (to pick up dinner), starting the Tahoe was absolutely perfect. Usually I have to kick the floor board, beat on the dash, or do some magic to get it to start (it had been this way for a few months). It was perfect. I was so stunned that I turned off the ignition and started it again - several times it was perfect. So, I stepped on the brake, released the emergency brake and the Tahoe died! It would not start until I beat on the floor enough. I got home (after some stuttering) and decided to take a look around the emergency brake. FOUND IT! There is a harness that sits right behind (above) the e-brake pedal assembly. It just so happens that one branch of that harness was resting on the top pivot point and this action of using the e-brake over the years wore a hole through the harness insulation and two pairs of CAN BUS wires! The wires were shorting on the rotating piece of release assembly! I wrapped each wire individually, re-wrapped the harness, and then zip tied it away from the pedal assembly - problem solved! This happened a year ago and it's been perfect ever since.

So... check this on your system, what you describe is in fact a CAN BUS shorting.

Thanks,
I cannot see behind the plastic cover. The moving parts above appear to be non interfering. Can I assume the movement behind the plastic footwell will expose more ? Where is the can bus and how large is it ? Thanks for your help.

 

[petethepug]

If not done yet, always, always, start with replacing the -\+ battery cables. They rot from the inside out. They may LK pristine but be rotten to the core inside.

After that you’ll have a good platform to work off of