GMC Troubleshooting Questions? Ask a Mechanic for Answers
What year and model is your GMC?
Just about anything electrical on your 2015 Denali is controlled by a computer, including the starter. The engine control module is what controls the starter function, as well as spark and fuel, so I would be attaching a scan tool to your truck to see what the computer is telling me.
This is under warranty, I assume, unless you're over 36k miles. If that's the case, have it towed to the dealer and let them handle it for you.
Did you get this worked out? Wanted to follow up and make sure you got what you needed from me.
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