I have always had this problem with my truck since I drove it off of the lot and now my warranty is out and I need to try and repair it myself. The problem is when I start up the truck I can see all of the lights on the 4wd push button panel light up for about 5-10 seconds and then they all go out. You cannot engage the truck into 4wd at all. I did some research online and found out that more than likely it was the actuator on the front passenger side that was the problem since the GMC part was a bad design and the recommendation was to buy an aftermarket one. I purchased the new actuator and I replaced it with hopes of it working. I installed it with the negative battery cable off in hopes of maybe some type of computer error that may also need to be reset. After all of this was done I am still having the exact same problem. Is there some type of sensor that is stopping the power from going to the actuator? I have checked all of the fuses under the dash and the hood to no avail. Is this something that the dealer will have to reset or can I do it with a code reader of some type? Thanks!