most likely the cable needs to be replaced
Latch —Liftgate
Removal
Disconnect the battery ground cable (14301).
Remove the liftgate trim panel. For additional information, refer to Section 501-05 .
On Navigator, remove the license plate bracket. For additional information, refer to Section 501-08 .
Separate the liftgate latch from the liftgate.
Remove the screws.
Separate the liftgate latch from the liftgate.
Disconnect the door open warning lamp electrical connector.
CAUTION: Be careful not to kink the liftgate latch control cable while disconnecting it.
Disconnect the liftgate latch control cable.
Remove the liftgate latch.
Installation
NOTE: When the battery is disconnected and reconnected, some abnormal drive symptoms may occur while the vehicle relearns its adaptive strategy. The vehicle may need to be driven 16 km (10 mi) or more to relearn the strategy.
To install, reverse the removal procedure.
If necessary, use Multi-Purpose Grease F5AZ-19G209-AA (aerosol) or equivalent meeting Ford Specification ESR-M1C159-A to lubricate the latch.
Handle —Liftgate
Removal
Remove the liftgate trim panel. For additional information, refer to Section 501-05 .
On Navigator, remove the license plate bracket. For additional information, refer to Section 501-08 .
Remove the liftgate latch remote control bolts and position aside.
On Expedition, remove the liftgate handle (43400).
Remove the two nuts.
Remove the reinforcement plate.
Remove the liftgate handle.
CAUTION: Use care when removing the liftgate handle to avoid breaking the plastic tangs.
On Navigator, remove the liftgate handle.
Disconnect the liftgate latch remote control rod.
Remove the nuts.
Remove the liftgate handle.
Installation
NOTE: Make sure the handle shaft and the driver on the liftgate latch controller are properly aligned.
NOTE: On Navigator, make sure the plastic tangs of the handle fully engage the holes in the sheet metal.
NOTE: On Navigator, make sure the liftgate latch remote control rod is not preloading the liftgate latch. It should be clipped in a relaxed state with no slack.
To install, reverse the removal procedure.