Hey I have had that happen a couple time, the 4wd solenoid is malfunctioning or stuck. Mine usually does it turning from 4low back to 2wd. Try putting the truck in neutral turn switch to 4wd low. Put in reverse or drive move for several yards, stop, foot on brake shift into Neutral. Move it to 4wd high, repeat process, (while doing this never put in park) put it in 2wd then drive it around for a few minutes then look to see if light is still flashing. Do you have a scan tool? (not a bully but like a matco or Snapon) you can go into the transmission/transfer case and test and reset solenoid. I usually get this light when I shift into 4wd low without putting it on (N). I forget only being able to only go into 4wd high. Try this and if you have no luck we have plan 2, in 2wd in park turn off truck. Unhook any programmer you may have and unhook battery (neg terminal only) for at least 3 minutes. Hook up battery and drive it and check the light. Hope all goes well!