Liftgate ajar where is the liftgate ajar switch located

more then likely it's a door ajar switch - not a sensor .
Anti-Theft- Perimeter Alarm System
The perimeter anti-theft system provides for vehicle security through an audible and visual notification if the vehicle's exterior is invaded without the system being shut off. The system self-arms when the doors, liftgate and hood are closed and the key is OFF. Any open door, hood or liftgate will prevent the system from arming. The hood ajar switch, door ajar switches and liftgate ajar switch cause these circuits to register as normally closed circuits. The vehicle security module monitors the status of the hood ajar, door ajar and liftgate ajar switches. If these circuits indicate an open entry point, the switch opens the circuit to the vehicle security module, which energizes the horn and autolamp relays (causing the horn to sound and the lights to flash). The vehicle security module turns off the anti-theft system when it receives a command through the keyless entry keypad, remote keyless entry (RKE) transmitter, or anti-theft alarm inhibit switch.
https://www.youtube.com/watch?v=egIGBzO065U

Does it have a power lift gate ? Do you know anything about automotive electrical systems ? How to use a wiring diagram along with a digital volt ohmmeter to test electrical circuits . ?
Power Liftgate
The power liftgate feature will allow the customer to automatically open or close the liftgate by activating the interior open/close switch, the remote keyless entry transmitter, or by manually initiating liftgate movement. The power liftgate uses a power cinch system to latch the liftgate.
The power liftgate system consists of:

• Power liftgate control switch (located in the overhead console)
• Power liftgate motors (located in the rear headliner area)
• Optical sensor and power liftgate encoder wheel (located in the left power liftgate motor assembly)
• Pinch strip switches (located on the body by the liftgate)
• Home position switch (located on the cinch actuator)
• Forkbolt switch (located on the cinching latch assembly)
• Detent switch (located on the cinching latch assembly)
• Liftgate close chime module (located in a unit external from the power liftgate module)

The forkbolt and detent switch are located on the cinch latch assembly and the home position switch is located on the cinch actuator assembly. For information on removal of the latch or cinch actuator assembly, refer to Section 501-14 .
The power liftgate may not operate under the following conditions:

• a low voltage or dead battery.
• a disconnected battery.
• a power liftgate that has been left open for more than six hours.
• a power liftgate that has been manually closed and left ajar.

If any of these conditions has occurred, the power liftgate must be reset before performing any pinpoint tests. For additional information, refer to Power Liftgate Initialization .

Power Liftgate Initialization NOTE: If the power liftgate system is turned OFF in the message center, the system cannot be activated with any switches or with the liftgate handle. The system will need to be turned ON for any power operation to occur.
NOTE: The power liftgate may not operate under the following conditions:

• a low voltage or dead battery.
• a disconnected battery
• a power liftgate that has been left open for more than six hours.
• a power liftgate that has been manually closed and left ajar.

If any of these conditions has occurred, the power liftgate must be reset.

1. Manually close and fully latch the power liftgate.

1. NOTE: If the power liftgate does not open during this step, refer to the symptom chart to diagnose the power liftgate for no operation. Power open the power liftgate by using the keyfob or overhead console switch.

1. Once the power liftgate is fully open, close the power liftgate by using the keyfob or overhead console switch.
2. your best bet mite be to have a qualified repair shop check it out .

liftgate ajar switch , possibly . Without testing that would be just a guess . Do you know how to test automotive electrical circuit's ? Using a wiring diagram an a DVOM -digital volt ohm meter ? Looking at a factory service repair manual to find location of the ajar switch . Also checking for DTC- diagnostic trouble codes ,first !
B2703 Open/Close Switch Stuck Active Power Liftgate Module B2721 Gate Ajar Output Short to Ground or Open Power Liftgate Module REFER to Section 501-03 . B2722 Open/Close Switch Active During Self-Test Power Liftgate Module REFER to Section 501-03 .
B2718 Gate Ajar Output Short to Battery Power Liftgate Module REFER to Section 501-03 .

• The interior lights remain on and the instrument cluster message center indicates liftgate ajar

• Liftgate latch is not in primary position.

• Manually PULL on the liftgate. If liftgate moves, OPEN and CLOSE the liftgate to the primary latch position. Manually PULL on liftgate glass. If liftgate glass moves, OPEN and CLOSE the liftgate glass. If the liftgate ajar condition still exists, Go To Pinpoint Test B .

PINPOINT TEST B: THE POWER LIFTGATE DOES NOT OPERATE/DOES NOT OPERATE CORRECTLY Test Step Result / Action to Take B1 RETRIEVE THE DTCs FROM POWER LIFTGATE MODULE

• Use the recorded power liftgate module DTCs from the continuous and power liftgate module self-tests.
• Are any power liftgate module DTCs recorded?

Yes
If DTC B2552 or B2698, GO to B54 .

If DTC B2699 or B2701, GO to B40 .

If DTC B2700 or B2702, GO to B41 .

If DTC B2703 or 2722, GO to B4 .

If DTC B2704, B2705 or B2706, GO to B31 .

If DTC B2709, B2710, B2711, B2712, B2819, or B2820, GO to B23 .

If DTC B2713, GO to B19 .

If DTC B2714, B2715, B2821 or B2822, GO to B15 .

If DTC B2718 or B2721, GO to B46 .

If DTC B2723, GO to B50 .

If DTC B2724 or B2725, GO to B10 .

If DTC B2726, GO to B35 .

If DTC B2825, GO to Symptom Chart and verify symptom the power liftgate reverses during power close operation (mid-travel). If sent here from the symptom chart, GO to B23 .

If the liftgate unexpectedly reverses direction when ambient temperatures are greater than 32°C (90°F), GO to B23 .

No
GO to B2 .

Door ajar switches maybe bad . Take the door panel off ,find a wiring diagram an test the circuit . Or you could check at the BCM ,would still need wiring diagram so you know what wire is what . Do you know how to test electrical circuits using a DVOM - digital volt ohm meter ? Could also take it to a qualified repair shop an have the BCM checked for DTC'S - diagnostic trouble codes .
The BCM, the door switches, and the liftgate module (LGM) (if equipped with power liftgate) communicate through the GMLAN serial data circuit for the lamp illumination commands of the doors, liftgate, and liftglass open/ajar switch signals. The LGM receives a ground signal from the pawl switch, ratchet switch, and liftglass ajar switch that are located within the liftgate latch and liftglass latch. For all vehicles, the left and right rear door latch switches are both on one circuit that is also an input to the BCM.
If the vehicle has a manual liftgate, there is an input circuit from the liftgate latch switch and liftglass latch switch directly to the BCM.
The left and right front door courtesy lamps receive voltage and ground from the driver door switch and the passenger door switch respectively. The remaining courtesy lamps are controlled and receive voltage through the BCM from the CTSY fuse in the instrument panel fuse block.

DTC B2555 01: Passenger Compartment Lamp Control Circuit Short to Battery
DTC B2555 02: Passenger Compartment Lamp Control Circuit Short to Ground

Unless you have electrical diagnostic skills , I suggest you take this to the dealer ! The lift gate can be opened by operating the switch on the instrument panel. Battery voltage is supplied to the liftgate actuator through the body control module (BCM). The BCM will pulse the lift gate actuator when a release input is received through the key fob, or the instrument panel switch.
The body control module (BCM) receives an input from the liftgate ajar assembly. The ajar assembly is normally open when the liftgate is fully closed. When the liftgate is opened, the ajar assembly contacts close providing a path to ground. The driver information center (DIC) illuminates the rear access open message when the gate is open. The instrument panel cluster (IPC) receives a serial data message from the BCM indicating the liftgate ajar status. If this message is displayed and the vehicle speed is greater than 8 km/h (5 mph), a chime will sound.
It could be ajar switch is bad .

It is inside the lift gate on the latch mechanism

https://s33.postimg.org/f0juccxm7/interior_lamps.jpg

Click on the link.
Found that fuse for interior lamps. It's located in the smart junction box.

The liftgate consists of the following components:

• liftgate door lock actuator
• liftgate lock cylinder (if equipped)
• liftgate window glass
• liftgate window latch/ajar switch
• liftgate window glass release handle
• liftgate latch remote control which consists of the following component:
  • liftgate release handle
• liftgate latch, which consist of the following component:
  • liftgate latch door ajar switch

Liftgate Latch Actuator Removal and Installation

1. Remove the liftgate latch remote control. For additional information, refer to Liftgate Latch Remote Control in this section.

SECTION 501-14: Handles, Locks, Latches and Entry Systems 2001 Escape Workshop Manual
REMOVAL AND INSTALLATION Liftgate Latch Removal and Installation

1. Remove the liftgate trim panel.

1. Disconnect the liftgate ajar switch electrical connector.

1. Disconnect the liftgate latch actuating rod.
   1. Open the clip.
   1. Disconnect the actuating rod.

1. Remove and discard the liftgate latch bolts.

1. Remove the liftgate latch.

1. NOTE: Make sure the liftgate latch release rod is not preloading the latch. It should be clipped in a relaxed state with no slack.
   NOTE: Position the liftgate latch release rod by pushing outboard to remove the slack.
   

1. Remove the screws and the liftgate latch actuator

tascafordparts.com for discount.

The liftgate actuator and remote control are in the liftgate.
The module is in the left rear quarter trim panel.


SECTION 501-03: Body Closures 2003 Expedition/Navigator Workshop Manual
REMOVAL AND INSTALLATION Power Liftgate Module Removal and Installation
NOTE: Prior to removal of the power liftgate module, it is necessary to upload module configuration information to a diagnostic tool. This information needs to be downloaded into the new power liftgate module once installed. For additional information, refer to Section 418-01 .

1. Remove the rear quarter trim panel. For additional information, refer to Section 501-05 .

1. Remove the power liftgate module.
   1. Disconnect the electrical connectors.
   1. Remove the bolts.

1. NOTE: Once the new power liftgate module is installed, it is necessary to download the module configuration information from the diagnostic tool into the new power liftgate module. For additional information, refer to Section 418-01 .
   

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Principles of Operation
The power liftgate is controlled by the power liftgate module.
The power liftgate module receives inputs from:

• glass position switch (determines the ajar status of the liftgate glass).
• forkbolt switch (determines the primary position of the latch).
• detent switch (determines the secondary position of the latch).
• home switch (determines the power cinch status).
• power liftgate control switch (activates the power liftgate from the interior of vehicle).
• pinch strip switches (determines if an obstacle is detected between the pinch strip and liftgate).
• instrument cluster module (activates and sets the options for the power liftgate).
• optical sensor (determines the direction, travel speed and obstacle detection of the liftgate).
• UBP serial communication link.

The power liftgate module sends outputs to:

• liftgate motors.
• power cinching latch system.
• liftgate chime module.
• body security module

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The liftgate consists of the following components:

• liftgate window glass latch
• door lock actuator (power liftgate only)
• liftgate latch
• liftgate handle
• liftgate latch remote control (power liftgate only)
• liftgate ajar switch
• chime module (power liftgate only)
• -------------------------------------------------

Normal Operation When any door or the liftgate is opened, the ajar switch provides a ground signal to the smart junction box (SJB). When the door or liftgate is closed, the ajar switch opens, removing the ground signal. The SJB uses the multiple inputs from the ajar switches to determine whether the doors or the liftgate are in the open or closed position. The SJB then provides a message to the instrument cluster over the communication network. The message center uses this information to display the door/liftgate ajar message.

I suspect your door switch is not closing all the way.