The 5.3 and 3.42 gears tells us you don't have the Max Tow package and your GCWR is 15,000 lbs. If your truck weighs 5,900 lbs on it's own, that leaves you with only 9,100 lbs for a trailer, passengers, and cargo. Advertised dry trailer weights rarely match actual trailer weights.
Either pick a smaller trailer, buy a bigger truck, or be sure to post on here anytime you're towing so that us responsible motorists can avoid encountering you on the road.
https://my.gm.com/content/dam/gmownercenter/gmna/dynamic/manuals/2015/chevrolet/equinox/CH-CAT-10217126_MY15 US Trailering Guide_122215.pdf