4wheel drive wont go in gear

Before you go spending money, here's what you should do.
On the passenger side, remove the right lower hinge trim panel (right next to the door) behind you'll find the 4x4 module.
disconnect the 2 plugs for about 30 seconds (module have tendency of locking up)
IMPORTANT... look at the plugs for signs of corrosion (very common)
if OK, then plug them back in and try to Switch to 4 hi.
If OK, no further action needed.
If not, then the system needs to be diagnosed, the module stores the failed code, and a scanner is a must. - Another thing to try is to reset the TCM (transfer case control module). Disconnect the ATC fuse in the under hood fuse block for 1 minute to clear the codes. Cycle the ingnition key on and off 5 times. Reinstall the fuse. Recheck 4x4 operation.
Use the Owner's Manual to manually go into neutral and reset to 2WD HI. But then look under the hood check the fuses or look for wiring that may have come unplugged.