I have a 2008 Silverado, 5.3, 4WD (obviously) and the service 4WD light came on. I changed the actuator, the problem "seemed" to go away. It was gone for 3 weeks. Went out today and the light is on again. But this time, it is stuck in 4 low. I tried shutting off the truck, waited and restarted it, still on. Unplugged the actuator, replugged it in, to make sure the plug was on completely and locked on. All good there, no corrosion on the contacts, any ideas???