I have a 99 ford expedition 5.4l with the full time 4wd system. Its been sitting for about a year and the battery was completely dead. This year I put a new battery in it and started it up and on the dash the 4x4 light was on even though the switch was set to the 4wd option. Its driving like its in 4wd and it wont shift into 4x4 or 4low. Any ideas on what wrong?