When pushing button for 4wheel drive, the amber flashes continully. does not go into 4wheel drive

It will eventually. most likely the electrical connections under truck got wet and stops the operation your explaining. My 03 yukon xl does this all the time. when i shut it off next day i start and it works. sometimes the 4 lo light comes on yet it is still in 2 hi. other days they all flash. somedays the red nuetral light is on yet i'm driving. Damn electronics. My ford explorer is the same way. I never get the underbody wash either as this leads to two days of flashing.