Rear doors unlock but will not lock - 2005 Chevrolet Silverado

The most likely culprit is a faulty actuator. You can test this by having someone activate the rear hatch while listening for a click or sound of some sort. If there is sound but no opening, it indicates a bad latch actuator. If there is no noise, it could be a fuse or wiring issue. You can manually unlock the door by removing the trim, but be careful around the glass latch as there are 2 push pins.

https://www.autogenius.info/chevrolet-suburban-2006-fuse-box-diagram-2/


Check the wiring in the boot that runs from the body to the top of the liftgate for broken wires.

You might have to take it to a collision shop. Remove the rear hatch panel to gain access to the latch assembly if it's not responding. If you can't get it open, take it to a collision shop as they deal with these kinds of things regularly.

Door Lock System Components
The power door lock system consists of the following components:
• Driver door module (DDM)
• Passenger door module (PDM)
• Door lock relay--Located in the instrument panel (I/P) fuse block and controls the locking of the rear doors.
• Door unlock relay--Located in the I/P fuse block and controls the unlocking of the rear doors
• Body control module (BCM)
• IP BEC
• Reversible door lock actuators in each door

Driver and Passenger Lock System Operation
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 monitor these inputs and send a LAN message indicating a change in the switch position. Modules, that activate the power door lock motors, receive the LAN message and activate the motor in the appropriate direction to lock or unlock the vehicle doors. The body control module (BCM) upon receipt of a lock or unlock signal will control the rear door lock or unlock relays and also send a LAN message to the DDM and PDM to perform the commanded function.
The modules that activate the power door lock motors are:
• DDM (driver door lock actuator)
• PDM (passenger front door lock actuator)
• BCM (both rear door lock actuators)
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 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. 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.

I imagine you checked the fuse.

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)

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The passenger door module (PDM)

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The body control module (BCM)

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The driver information center (DIC)

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The rear door lock switch

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The door lock relay

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The door unlock relay

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The liftgate lock relay--utility vehicles with liftgate only

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The reversible door lock actuators in each of the doors and liftgate

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LOCKS 20A fuse (rear lock/unlock relay supply voltage)

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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:
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A power door lock or unlock switch activation

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A keyless entry transmission

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An automatic door lock function

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A delay lock function

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Door lock cylinder switch activation

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Lockout Prevention

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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:
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The DDM (driver door lock actuator).

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The PDM (passenger front door lock actuator).

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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

Door Lock System Components
The power door lock system consists of the following components:
?€¢
The driver door switch (DDS)

?€¢
The passenger door switch (PDS)

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The body control module (BCM)

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The driver information center (DIC)

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The rear door lock/unlock relay (LBEC)

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The door lock actuators in each of the doors The rear passenger 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.
Do you know what the BCM is , body control module ! If you do not know about this stuff I strongly suggest you to it to a ASE certified repair facility ! Save yourself some money an aggravation !

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

The rear doors probably dont come w accuators in them. Meaning that the rear doors alot of times don't have power options. If you are certain that your rear doors have factory power locks then I would say it's a wire somewhere...did you try a double click of the unlock button. My two door chevy truck unlocks the driver door with one click and the pass door requires a double click. Hope this helps !

Doesn't lock or unlock ? These relay's are controlled by the BCM - body control module .
I have factory service repair information , 32 steps ! Too much info to post here .

Power Door Locks Inoperative (Rear Door(s))
2
Activate the door lock switches to the lock and unlock positions.
Do both rear passenger doors lock and unlock?
YES - Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
NO - Go to Step 3
3
Is there only one door lock actuator that is inoperative?
YES - Go to Step 6
NO - Go to Step 4
4
Are the rear door lock actuators inoperative for both lock and unlock?
YES - Go to Step 8
NO - Go to Step 5
5
Do the rear door lock actuators lock?
YES - Go to Step 15
No - Go to Step 10
6
Disconnect the inoperative 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 7
NO - Go to Step 25

Some of these steps can be bypassed because you say they worked after replacing the relay .LOCK RELAY ? right .

7
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 24
NO - Go to Step 26
8
Remove the rear door unlock relay.
Connect a test lamp to battery positive voltage.
Probe the door actuator unlock control circuit cavity in the left IP fuse block.
Does the test lamp illuminate?
YES - Go to Step 21
NO - Go to Step 9
9
Install the rear door unlock relay.
Remove the rear door lock relay.
Connect a test lamp to battery positive voltage.
Probe the door lock actuator lock control circuit cavity in the fuse block.
Does the test lamp illuminate?
YES - Go to Step 20
NO - Go to Step 22
10
Remove the rear door lock relay.
Connect a test lamp to a good ground.
Probe the battery positive voltage circuit (high current) cavity in the fuse block.
Does the test lamp illuminate?
YES - Go to Step 11
NO - Go to Step 22

If your not familiar with GM diagnostic flow chart's , they can be confusing .
Let me know if you need more diagnostic steps .

sequence for freelander lock unlock, to lock 1press = door lock , 2press = door dead lock , to unlock 1 press = driver door unlock, 2 press = passenger doors unlock, also rear window can be operated from fob to do so press and hold unlock button for 3 or more seconds and rear window will roll down.neat feature.hope this helps

sounds like that rear door lock will also not unlock with the switch either, correct ? It might lock , but not unlock. Door lock actuator needs to be replaced.