2015 Yukon XL Denali Intermittent Brake Light Outage

[Jenn & Chris Carter]

Hey experts, I've got a 2015 Yukon XL Denali that's been having some quirky electrical events on occasion...various (unwarranted) warning messages on the dash display, and twice while at low speeds in a parking lot the car has had the dash lights flicker/blink and then the car died.  Once on an interstate on ramp it seemed like every electrical component started going crazy and the car felt like it was stalling out for a few seconds before it all stopped as quickly as it started.  I'm also experiencing the brake lights not working at times.  I've had a few people wave me over to let me know that the right or left one is out, but it seems like they've never both been out at the same time.  

 

At first I only was aware of the right brake light intermittently not working and thought maybe it was the common issue of the wire breaking, I was about to pull the light and re-solder it when someone told me that the right was working and it was the left that was out.  Since then we've realized that it is intermittent at best that either the right or left will be out for a time.  My husband thinks that it's likely the alternator not keeping up with all the electrical draw that is making the different things act up.  We got a voltage reader for the front cigarette lighter port and I've been keeping an eye on my voltage. It hovers between 13.8 and 14.7.  

 

Is there something else that we are overlooking that could be the culprit? I appreciate any input. Thanks.

[SARNCAN]

Hey experts, I've got a 2015 Yukon XL Denali that's been having some quirky electrical events on occasion...various (unwarranted) warning messages on the dash display, and twice while at low speeds in a parking lot the car has had the dash lights flicker/blink and then the car died.  Once on an interstate on ramp it seemed like every electrical component started going crazy and the car felt like it was stalling out for a few seconds before it all stopped as quickly as it started.  I'm also experiencing the brake lights not working at times.  I've had a few people wave me over to let me know that the right or left one is out, but it seems like they've never both been out at the same time.  
 
At first I only was aware of the right brake light intermittently not working and thought maybe it was the common issue of the wire breaking, I was about to pull the light and re-solder it when someone told me that the right was working and it was the left that was out.  Since then we've realized that it is intermittent at best that either the right or left will be out for a time.  My husband thinks that it's likely the alternator not keeping up with all the electrical draw that is making the different things act up.  We got a voltage reader for the front cigarette lighter port and I've been keeping an eye on my voltage. It hovers between 13.8 and 14.7.  
 
Is there something else that we are overlooking that could be the culprit? I appreciate any input. Thanks.

Check battery terminals and make sure they are tight and clean, if so, you may need to replace the battery size R94 (make sure you take 80Amp battery and absolutely nothing less than 80)

Regarding the tail light, it is common that Yukon LED tail light fail, and you need to fix it if you are out of warranty.

Here is how to fix:

[cs15dah]

Agree. Sounds like a grounding issue. I’d be checking all the grounding points, starting with ensuring the battery lugs are tight. Also check to ensure all the wiring harness plugs are snug. Being so intermittent, sounds like a connection somewhere is constantly breaking contact. 
 

Sounds like the tail light problems are a separate issue. 

[Jenn & Chris Carter]

Thank you both, I'll work on checking terminals and grounds.  I forgot to mention that we did change the battery during this process but it makes sense that if the wiring/terminals are not right the problem would persist with a new battery.  I'll be checking the tail lights for that issue as well. 

[Tahoe02]

You can do a Google search. There is a company and maybe more than one that will repair the tail light. Obviously it would be less expensive to make the repair yourself. Good luck.