Can unlock doors manually , but liftgate will not open. Can liftgate be unlocked manually?

Service repair info. manual would be the place to start ,seeing how you have no clue .,or maybe a qualified repair shop. How are you going to fix it with out knowledge of how it works an what to check , --------------------------------------------------------------------------------
Power Door Locks Circuit Description
The power door locks are operated by reversible motors. The motors are found in the following locations:
• In each front door
• The side door
• The rear door
The PWR ACCY circuit breaker (30A) supplies voltage to the door lock motors.
If you move either power door lock switch, mounted in the front doors, the LOCK applies voltage to cavity F of the door lock relay. This energizes the lock coil in the relay. Current then flows through CKT 295 (GRY) directly to the following components:
• Both front door lock motors
• The side door lock motor
• The rear door lock motor (cargo doors only)
CKT 246/294 (TAN) provides the ground for the motors. The normally closed contacts of the UNLOCK then contacts the door lock relay.
If you move one of the door lock switches to UNLOCK the polarity of the system reverses. Current flows through the energized UNLOCK relay contacts. The LOCK relay contacts provide ground.
When the UNLOCK button is pressed once on the RKE transmitter, only the driver door unlocks. If it is pressed a second time within 5 seconds, all doors unlock.
If the side door is open, the side door jamb switch ground signal is opened/broken. If you move the door lock switch to LOCK while the side door is open, the following actions occur:
• The 2 front doors lock
• The rear door locks (cargo doors only)
When you close the side door, the door jamb switch closes. This closes the ground signal to the body control module {CKT 775 (PNK)}. A 5 second timer then starts in the module. After 5 seconds, cavity A4 connector C1 of the body control module supplies voltage to the door lock relay via CKT 195 (LT BLU). This energizes the door lock relay, which sends voltage to the door lock motors in order to lock the side door. Refer to Door Jamb Switches, Liftgate Strut Switch for a schematic of all door jamb switch inputs.
If the side door opens during this 5 seconds, the 5 seconds timer is reset. The locking pulse takes place at the end of the 5 seconds. Unlocking the door resets the 5 second timer in the body control module.
Use the following components in order to unlock the door lock system:
• The LH power door lock switch
• The RH power door lock switch
On vehicles equipped with cargo doors, the cargo door opener mechanically opens the door once the door lock system is unlocked. On vehicle equipped with a liftgate, the liftgate lock/unlock release switch (mechanical key) is added in order to serve the same function as the front power door lock switches. These functions locking and unlocking all doors, including the liftgate. Once the door lock system is unlocked, press the liftgate release switch in order to electrically open the liftgate and pull the handle in order to open the secondary latch.

2008 Saturn Vue liftgate will not open

The endgate/liftgate can be locked or unlocked by operating either one of the front door lock switches, your's doesn't do this ?
Endgate/Liftgate
Once the vehicle doors have been unlocked, the endgate/liftgate can be opened by using the handle mounted to the exterior of the gate. The endgate/liftgate can be locked or unlocked by operating either one of the front door lock switches, or by pressing the Lock/Unlock button on the key fob. The endgate/liftgate lock and unlock functions operate in conjunction with the rear doors.

The rear hatch locking is computer contolled .
The BCM also runs diagnostics on the liftgate lock relay control circuit and will set DTC B3825 as current and also send a Class 2 message to the DIC. The DIC will display REPLACE LIFTGATE FUSE to inform the driver that a fault has been detected in the liftgate lock circuit and that the liftgate is not locked. Faults that will set the DTC and cause the DIC to display the message could be any of the following:
• An open ECC fuse
• An open or short to ground in the liftgate lock relay battery positive voltage circuit
• A faulty liftgate lock relay
• An open or short to ground in the liftgate lock relay control circuit
• A short to ground in the liftgate lock actuator lock control circuit
• A faulty BCM

The liftgate lock relay supply and coil sides receive a constant voltage through the battery voltage supply circuit and the ECC fuse. The normally closed contact is connected to ground and the control side is connected to the body control module (BCM). A lock function will occur when a door lock switch activation, keyless entry lock transmission, auto door lock function or a liftgate lock function has been received by the BCM. The BCM will then ground the control side of the liftgate lock relay. This energizes the relay and allows voltage to be applied to the liftgate lock actuator lock control circuit. Since the other side of the liftgate lock actuator is connected to the normally closed contacts of the door unlock relay to ground, the liftgate will lock. When an unlock function occurs the BCM will ground the control side of the unlock relay and the rear doors and liftgate will unlock.
The power door lock system consists of the following components:
• The driver door module (DDM)
• The passenger door module (PDM)
• The body control module (BCM)
• The driver information center (DIC)
• The rear door lock switch
• The door lock relay
• The door unlock relay
• The liftgate lock relay--utility vehicles with liftgate only
• The reversible door lock actuators in each of the doors and liftgate
• LOCKS 20A fuse (rear lock/unlock relay supply voltage)
• ECC 10A fuse (liftgate lock relay supply voltage)

If i were to guess i would say you mite need a new lock actuator , but i don't guess . You could take the hatch inside panel off an check for B+ voltage for the lock actuation as someone pushes the switch . Or have it checked for codes .

There are actually three relays , an there are controlled by the BCM - body control module !
When a door lock switch is activated in the lock or unlock position the BCM will receive a voltage signal on either the door lock switch lock or unlock signal circuits.
The BCM, upon receipt of a lock switch lock or unlock signal, will switch the appropriate lock relay control circuits to battery positive voltage. This will energize the appropriate lock or unlock relays. The relay will supply voltage to the door lock actuator lock or unlock control circuits to one side of the lock actuator. Since the opposing side of the lock actuators are connected to ground through the other lock actuator control circuit and the normally closed contacts of the lock or unlock relay, the doors and liftgate will then lock or unlock appropriately.
Three relays are used to operate the locks. DRV DR UNLCK relay, PASS DR UNLOCK and DR LCK relay. This is done to isolate the driver door lock actuator so it can be unlocked by itself using the keyless entry transmitter.
Rear Hatch/Gate Description and Operation
The liftgate 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 liftgate actuator when a release input is received through the key fob, or the instrument panel switch.
Door/Lift gate Latch Assembly

1. Install a 20-A fused jumper wire between the control terminal 3 and 12 volts. Install a jumper wire between the ground terminal 2 and ground.
2. Verify the actuator turns on & off.

?‡'
If the function does not perform as specified, replace the applicable door latch.

They have a history of this problem. Likely something is stuck in the lock mechanism.... dealers can pop this open for you. It happened to my Explorer once. Couldn't get her open, found a piece of towel stuck in mechanism of liftgate lock

To unlock the liftgate, press the unlock button on the Remote Keyless Entry (RKE) transmitter twice or use the power door lock switch.
To lock the liftgate, press the lock button on the RKE transmitter or use the power door lock switch. The liftgate does not have a key lock cylinder.
To open the liftgate, pull up on the handle located in the center of the liftgate.
When closing the liftgate, use the molded handles to pull the liftgate down. Push the liftgate closed until it latches.

The latch is seized. You will have to manually unlock it by removing the panel on the inside of the liftgae.

Take the liftgate inside panel off an check the wiring , connections etc....
rear door hatch lock repair GMC Chevrolet
chevy tahoe lift gate not opening
The liftgate will lock any time the vehicle is shifted out of park on vehicles equipped with an automatic transmission and at vehicle speeds exceeding 5 kph with manual transmission. This happens in conjunction with auto door locks if enabled or independently of auto door locks if the feature is disabled. This ensures that the liftgate is locked anytime the vehicle is shifted out of park or when the vehicle is in motion.
The liftgate lock relay supply and coil sides receive a constant voltage through the battery voltage supply circuit and the ECC fuse. The normally closed contact is connected to ground and the control side is connected to the body control module (BCM). A lock function will occur when a door lock switch activation, keyless entry lock transmission, auto door lock function or a liftgate lock function has been received by the BCM. The BCM will then ground the control side of the liftgate lock relay. This energizes the relay and allows voltage to be applied to the liftgate lock actuator lock control circuit. Since the other side of the liftgate lock actuator is connected to the normally closed contacts of the door unlock relay to ground, the liftgate will lock. When an unlock function occurs the BCM will ground the control side of the unlock relay and the rear doors and liftgate will unlock.
The BCM also runs diagnostics on the liftgate lock relay control circuit and will set DTC B3825 as current and also send a Class 2 message to the DIC. The DIC will display REPLACE LIFTGATE FUSE to inform the driver that a fault has been detected in the liftgate lock circuit and that the liftgate is not locked. Faults that will set the DTC and cause the DIC to display the message could be any of the following

Power Door Locks Inoperative - Endgate/Liftgate

Schematic Reference: Door Lock/Indicator Schematics
Connector End View Reference: Power Door Systems Connector End Views
1
Did you perform the Diagnostic System Check - Vehicle?
YES - Go to Step 2
NO - Go to Diagnostic System Check - Vehicle in Vehicle DTC Information
2
Activate the door lock switches to the lock and unlock positions.
Do both rear passenger doors lock and unlock?
YES - Go to Step 3
NO - Go to Power Door Locks Inoperative
3
Did the liftgate lock actuator lock and unlock?
YES - Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
NO - Go to Step 4
4
Disconnect liftgate door lock actuator.
With a test lamp connected to a good ground, probe the door lock actuator lock circuit at the door lock actuator harness connector.
Activate a door lock switch to lock position.
Does the test lamp illuminate?
YES - Go to Step 5
NO - Go to Step 7
5
With a test lamp connected to a good ground, probe the door lock actuator unlock circuit at the door lock actuator harness connector.
Activate a door lock switch to unlock position.
Does the test lamp illuminate?
YES - Go to Step 6
NO - Go to Step 8
6
Inspect for poor connections at the harness connector of the door lock actuator. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?
YES - Go to Step 10
NO .. Go to Step 9
7
Repair the open door lock actuator lock circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
YES - Go to Step 10
--
8
Repair the open in the door lock actuator unlock circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?
Go to Step 10
--
9
Replace the liftgate door lock actuator. Refer to Door Lock Actuator Replacement in Body Rear End.
Did you complete the repair?
Go to Step 10
--
10
Operate the system in order to verify the repair.
Did you correct the condition?
System OK
Go to Step 2

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