need help fast wont gointo 4x4

anyone ever have a problem like this i have a 2001 chevy dually 4x4 i just notice the SERVICE 4X4 LIGHT on tryed too put it into 4x4 and it wont go into 4x4 now? ANYONE HAD THIS PROBLEM? PLEASE LET ME KNOW THANKS ALOT

I had that problem with my 2000 4x4.
The 4x4 selector switch had to be replaced.

Paul.

just pull your instument panel part of the dash out--it just clicks out, pull the transfer case selector switch out, and replace it. Did it last week--$54 switch at a dealership, and about five minute repair on your own.

get it scaned at the dealer. the switch might be the problem or it could be the module or encoder motor. i don't know if your truck qualifies but gm's was having some problems with the encoder motors and has updated parts. you could also try disconecting the battery and touching the terminals together for 30s. if you have a diesel unhook both batterys this resets the module and 90% of the time the 4X4 will work again.