Humming behind the dash board and truck won't start, what is the humming

Hi, my name is Devin. I am an auto repair expert with the Car Genius team here at RepairPal. I'm sorry to hear you're having trouble with your vehicle. The humming sound you're hearing behind the dashboard of your Sierra 2500 HD, along with the truck not starting, could indicate an issue with the electrical system. It's possible that a component like the fuel pump relay, blower motor, or an electronic module is malfunctioning, causing it to hum continuously. This could be discharging the battery while the truck is turned off. You can inspect the connections around the dashboard for loose wires or components. If these steps don’t resolve the issue, it might be best to consult with a trusted repair shop that can diagnose the problem more thoroughly. If you need more advice, have any other questions about your vehicle, or would like to get connected to a RepairPal Certified shop near you, we have you covered. Give us a call at 877-913-1554, and we will happily help you out!