My liftgate doesn't unlock with either the door locks or keyless. All the other doors work fine. Is there a fuse that controls just the rear liftgate?

Power windows don't use fuse's , has circuit breakers
• PWR WDO CB 25A (fuse block) (System power for left and right windows 2-door vehicles. System power for LF and LR windows 4-door vehicles)
• PWR WDO CB 25A (IP wiring harness junction block) (System power for RF and RR windows 4-door vehicles)

Door Lock System Components
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)

The Lock's lock from the door switches ? If they do it's not a fuse problem . Which of these does your vehicle have ?
Keyless Entry System Description and Operation (with Accessory 2 Way Remote)
Keyless Entry System Description and Operation (without Accessory 2 Way remote)

The keyless entry system is a vehicle entry device. The keyless entry system is used in conjunction with the body control module (BCM) to remotely activate certain vehicle features. Keyless entry will lock/unlock the doors/liftgate when a corresponding button on the keyless entry transmitter is pressed. This is accomplished by the transmitter sending a radio frequency to the remote control door lock receiver (RCDLR). The RCDLR interprets the signal and activates the requested function via a serial data message to the BCM. A low transmitter or vehicle battery or radio frequency (RF) interference from aftermarket devices, such as 2-way radios, power inverters, computers, etc., may cause a system malfunction. High RF traffic areas may also cause interference that could lead to a malfunction. Keyless entry allows you to operate the following components:
• Door locks
• Liftgate lock
• Vehicle locator/Panic alarm
• Illuminated entry lamps
• Remote vehicle start
The keyless entry system has the following components:
• Keyless entry transmitters
• Keyless entry antenna
• 2 Way Advanced Remote Start RCDLR
• BCM

Your best bet , take it to a GM dealer .

None < LGM - liftgate control module inside the lift gate does .
Rear Wiper/Washer System Components
The rear wiper/washer system consists of the following components:
• Rear window wiper motor
• Rear washer pump
• Rear wash relay
• Rear wiper/washer switch
• RR WIPER Circuit Breaker 15A / ENDGLASS REG Circuit Breaker 30A
• WASH 20A fuse
• Body control module (BCM)
• Liftgate control module (LGM) / End gate module (EGM)

Your best bet , take it to a qualified repair shop. You have no idea of the complexity of these system's . Communication network between modules etc..... Could have DTC'S diagnostic trouble code's stored in the liftgate control module . An auto parts stores can not read these codes .

Power Door Lock Operation
The power door lock switches are integral components of the DDM and PDM. The switches are two position normally open rocker switches. When placed in either the lock or unlock positions, the switches provide a direct input to the DDM or PDM. The DDM or PDM monitors these inputs and sends a Class 2 message indicating a change in the switch's respective position. Modules which activate the power door lock motors receive the Class 2 message and activate the motor in the appropriate direction to lock or unlock the vehicle's doors and liftgate. The modules which activate the power lock motors are:
• DDM (driver door lock actuator).
• PDM (passenger front door lock actuator).
• BCM (both rear door lock actuators).
• LGM (liftgate door lock actuator).
The DDM, PDM and LGM are directly connected to the respective door lock actuator through the door lock motor lock and unlock circuits. Once a door lock or unlock request has been received, the module will supply battery voltage to one side of the actuator and ground the other causing the doors to lock or unlock.

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.

Gremlins ! HA HA HA sorry ! First off a little bit on how they work an what all is involved in making them work ! There are a few control modules in the mix , switches ,relays etc...
Door Lock System Components
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)

Door Lock System Controls
The power door lock system can be controlled by any of the following:
?€¢
A power door lock or unlock switch activation

?€¢
A keyless entry transmission

?€¢
An automatic door lock function

?€¢
A delay lock function

?€¢
Door lock cylinder switch activation

?€¢
Lockout Prevention

?€¢
An airbag deployment

The front power door lock switches are integral components of the driver door module (DDM) and passenger door module (PDM). The switches are two position normally open rocker switches. When placed in either the lock or unlock positions, the switches provide a direct input to the DDM or PDM. The DDM or PDM monitors these inputs and sends a Class 2 message indicating a change in the switch's respective position. Modules which activate the power door lock motors receive the Class 2 message and activate the motor in the appropriate direction to lock or unlock the vehicle's doors and liftgate. The rear door lock switch provides a lock and unlock signal to the body control module (BCM). The BCM upon receipt of a lock or unlock signal will control the rear door lock relays and also send a Class 2 message to the DDM and PDM to perform the appropriate function.
The modules which activate the power lock motors are:
?€¢
The DDM (driver door lock actuator).

?€¢
The PDM (passenger front door lock actuator).

?€¢
The BCM (both rear door lock actuators and cargo door/liftgate).
The DDM and PDM are directly connected to the respective door lock actuator through the door lock motor lock and unlock circuits. Once a door lock or unlock request has been received, the module will supply battery voltage to one side of the actuator and ground the other causing the doors to lock or unlock.
The rear passenger and cargo doors differ slightly in that they use lock and unlock relays. The relays supply and coil sides receive a constant voltage through the battery voltage supply circuit. The normally closed contacts are connected to ground and the control side is connected to the BCM. Once a door lock or unlock request has been received by the BCM, the BCM will ground the control side of the appropriate relay. This energizes the relay and allows voltage to be applied to either the door lock motor lock or unlock circuits. since the other side of the door lock actuator is connected to the normally closed contacts of the opposing relay to ground, the doors lock or unlock.
The first place to start is have a factory or equivalent scan tool hooked up , one that can read BCM DTC'S - diagnostic trouble codes ! This could lead to a fix faster ! Watch these three videos !
Door Locks Go Crazy 1

Do the power windows work ? DDM - driver door module fuse 15 amp - location is the instrument panel fuse box , plus LT DR circuit breaker 25 amp. Circuit breakers rarely go bad . The power locks are controlled by electronic's .The passenger side has another power supply ,that's why they still work .
Door Lock System Components
The power door lock system consists of the following components:
• The driver door switch (DDS)
• The passenger door switch (PDS)
• The body control module (BCM)
• The driver information center (DIC)
• The rear door lock/unlock relay (LBEC)
• The reversible door lock actuators in each of the doors and liftgate

The front power door lock switches are integral components of the driver door module (DDS) and passenger door module (PDS). The switches are 2 position normally open rocker switches. When placed in either the lock or unlock positions, the switches provide a direct input to the DDS or PDS. The DDS or PDS monitors these inputs and sends a LAN message indicating a change in the switch's respective position. Modules which activate the power door lock motors receive the LAN message and activate the motor in the appropriate direction to lock or unlock the vehicle's doors and liftgate. The rear door lock switch provides a lock and unlock signal to the body control module (BCM). The BCM upon receipt of a lock or unlock signal will control the rear door lock/unlock relay and also send a LAN message to the DDS and PDS to perform the appropriate function.
The modules which activate the power lock motors are:
• The DDS (driver door lock actuator)
• The PDS (passenger front door lock actuator)
• The BCM (both rear door lock actuators and cargo door/liftgate)
The DDS and PDS are directly connected to the respective door lock actuator through the door lock motor lock and unlock circuits. Once a door lock or unlock request has been received, the module will supply battery voltage to one side of the actuator and ground the other causing the doors to lock or unlock.
The rear passenger and endgate doors are controlled by the BCM through the rear door lock/unlock relay which is incorporated onto the printed circuit board in the LH BEC. The BCM controls the unlock relay by providing ground to energize the coil and controls the lock relay by providing battery voltage to energize the relay coil. The energized the relay and allows voltage to be applied to either the door lock motor lock or unlock circuits. Since the other side of the door lock actuator is connected to the normally closed contacts of the opposing relay to ground, the doors lock or unlock.

It's possible you have broken wire or wires inside the flex boot from the body of the vehicle to the driver's door . This happens a lot .
Fuse Block - I/P instrument panel
Left of the I/P behind the side trim panel

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

if it was mine I would take the rear inside door panel off and see if there is any rust or bind in the power door lock motor itself and also make sure that no one has broken a key off or stuck anything in the lock cause I had an expedition with this same problem and it was a broken key in the lock