I had the same problem with my '07 and found out about a vacuum switch that could be bad. My light would come on but while troubleshooting it I seem to remember that when I took the electrical connector loose on the switch, the light didn't come on then. I may be wrong, but I replaced the switch and it fixed my problem of not having 4wd. Mine would work sometimes and not at other times (it never worked when I needed it). The switch is located behind the battery on the firewall and cost about $26 at a local parts store.