My silverado 1500s 4wd switch is lighting up when you first start the truck but does not stay lit, my truck is stuck in 4lo and runs just fine, tried a new selector switch but that didn't change anything. I've heard some talk about the transfer case control module but I've also heard that that can get kinda spendy. I have also tried pulling the atc and 4wd fuses but they're fine. Any help would be nice, thanks