I've got the same truck and this happend to me the other day. For some reason the relay in the fuse box by the battery worked it's way out. I pressed it in and all was good.
FYI. I orginally was disconnecting the battery in a hope that this was magically going to clear some error that was causing the lights to come on, when I decided to look in the fuse rail. (I've worked with Windows (TM) computers for too many years I guess.) I actually don't know if you have to unhook the battery but I did both at the same time so not sure.
My first thought was that one of the ABS sensor wires were disconnected, you might want to check each of them. You can find them by the brake lines in the hub, they each have a connector next to the wheel well. Mine were all fine but you may find something.