Hub lock Operation

WARNING: This page is about a different car, the 2009 Ford Pickup, 2009 Ford F550 Super Duty, 2009 Ford F450 Super Duty, and 2009 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.

With the hub locks in the AUTO position, the 4WD ESOF system uses timed vacuum sequences to lock and unlock the wheel ends when switching the instrument panel MSS between 2WD and 4WD modes. A high vacuum level (222 mm [8.75 in] Hg and greater) is applied to the hub locks to lock the internal spring mechanism that engages (locks) the hub locks for 4WD mode, and a lower vacuum level (114 to 184 mm [5.9 to 7.1 in] Hg) is applied to unlock the spring mechanism that disengages (unlocks) the hub locks for 2WD mode. The vacuum signals are supplied to the hub locks by system components, including the 4X4 control module, wiring harness, solenoid, vacuum harness and vacuum seals. As a first step in service, eliminate obvious items such as loose wiring connections, loose vacuum connections or damaged vacuum lines.