poltergeist in the electrical system

[Dennismenace]

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.

 

[Discodisco]

Semi dumb question but did you load test the battery and check alternator is charging properly?

 

[Marky Dissod]

Was driving on misfire damaging other plug, coils causing the system to go into a limp mode?

1. Likely no.
2. Almost sure this is a random symptom of your actual electrical gremlin problem.

You may have intermittently good/bad connections. If you wiggle a wire loom and replicate the problem that way,
that wire loom has at least one wire that is contributing to the problem.

I'm sure someone here will come up with a more powerful test.

 

[Doubeleive]

ideally we need more info
mileage?
maintenance history?
rust?
typical things to check, besides grounds
battery cables, fuse box, ecm harness (water intrusion/rust/corrosion)

 

[JimDrew]

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.

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.

 

[Doubeleive]

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.

have a picture of this area? is it under the dash, under the body?

 

[JimDrew]

I actually have video of it. This forum won't accept video directly, so I will have to setup a video source of some kind.

Look at your e-brake pedal assembly. Crawl under the dash and grab the RELEASE handle and pull it. You will notice a cable that is connected to a spring loaded pivot point that releases the brake pedal when it is depressed. If you pull that handle over and over again, you will see it rotate back and forth as you pull and release. THAT is exactly where my wiring harness was resting. That little metal bar that flips back and forth was digging into the harness. Eventually it gouged through the black plastic insulation wrap that is around the harness and then into two pairs of the twisted CAN BUS wires. In my video you can see the exact problem. The solution is to fix the wires - I insulated the CAN BUS wires with black tape, and then wrapped the entire harness again with tape. I then took a zip tie and tied that branch of the wiring harness that was resting on the assembly up to the main harness. This moved the harness that was the problem about 3" away from where it was. Now there is absolutely nothing even remotely close to that the pivot point.

 

[JimDrew]

Here is a link for a temporary video. I just joined the 3 videos I took of the issue and fix. I will keep this video up on my server until I make another post with a proper video and more permanent link (and then edit this message accordingly):

https://www.otafw.us/TAHOE/tahoe_01.mp4

There should NEVER be a harness resting on top of the e-brake pedal assembly. This may not be the source of the OP's particular issue, but the issues with the dash going crazing, stalling, etc. are all CAN BUS issues and they are not that uncommon apparently. I would recommend everyone take a peek under their dash because I can't have the only '08 Tahoe LTZ that GM released where this occurred!

It was a fluke that I even found the source of this problem - the dealer could not track it down and they actually gave up (even knowing what the cause was) because they just couldn't find it.

 

[donjetman]

download to youtube and provide us the link here.

 

[mikez71]

The e-brake area and a few others are in a service bulletin.. (with photos)

https://static.nhtsa.gov/odi/tsbs/2012/SB-10043829-6448.pdf