Grounding was my issue in my wifes 2015 Silverado. Watch the video posted near the beginning of this post. It's very helpful. you can gain descent access to ground studs on both sides by 1) removing a pillar covers 10MM ratchet, 2) removingdash, front pop-in panel only (easy to pop off once a-pillar platic is removed), 3) remove the speakers and now i used an offset wrench to get the ground screws off. (don't drop them!!) Clean up the terminals, trim back the insulation and prob was solved. the pics show the smoking gun. Good Luck!