Manual Override
WARNING: This page is about a different car, the 2004 Ford Pickup, 2004 Ford F550 Super Duty, 2004 Ford F450 Super Duty, 2004 Ford Excursion, and 2004 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
The hub locks have manual override selector dials which, when rotated to the "lock" position, will keep the mechanism locked regardless of the instrument panel 4X4 mode switch position. Verify that both dials are in "auto" before evaluating ESOF operation.