My truck is a 2014 sierra denali white diamond ,the stock headlights/tail lights suck real bad just like others have complained,so I decided to change them to the 2016 denali lights.I bought the pair of led headlights and forward harness from GM and did the install myself(automotive tech),the lights turned on with the key in the run position but as soon as I started the truck the led headlights turned off,i was disappointed.I drove like that for a week trying to figure out the cause,what I noticed was when the voltage dropped below 12volts, the leds worked perfectly,tried to do a reflash at the dealer but no luck.Did some googling about led headlights and they all had one thing in common,LED CAN-BUS decoders.So I installed a pair and bingo,everything is fine except that in the daytime the DRL dosent turn off when I signal but that dosent bother me.I also changed the rears to 2016 LED tail lights.