i have a 06 1500 z71, the 4wd will say service 4wd after i go over a bump and when after i shut it off and turn it on it is in 4wd, and i have to switch it back, sometimes it will show both 4wd hi and 2wd lights on the switch or the switch will go blank, I have changed the switch and the wire harness and actuator is no more then 5k miles old, anyone have any ideas???