My back L/H door won't lock with remote central locking

The most common reason for a central locking to re-open on the lock button is the central locking has detected a door or the trunk isn't closed correctly. Open each door and the trunk to check there is nothing in the latch to 'trip' the unlock setting. Close the doors and trunk and retest the remote.
If this doesn't fix the issue have the wiring to the central locking check ed for loose connections or damaged wiring.

Sorry Andrew , no BCM on this vehicle . The Central Security Module is incharge of power door locks . Central Security Module For additional information, refer to Section 419-10 .
The central security module is equipped with a battery back-up which holds the programmed transmitter(s) memory in the event of the vehicle battery disconnection.
Principles of Operations The Door Switch Lock Function When a door lock switch is moved into the lock position or a door lock cylinder is rotated to the lock position, the door lock switch grounds the lock circuit input to the central security module. The central security module then provides 12 volts to one side of the door lock actuators contained in the door latch unit and simultaneously grounds the other side of the door lock actuators. This completes the door lock actuator circuit, causing the door lock actuators to rotate a cam assembly, which then locks the doors.

The Door Switch Unlock Function When a door lock switch is moved into the unlock position, the door lock switch grounds the unlock circuit input to the central security module. The central security module then provides 12 volts to the opposite side (relative to locking the door) of the door lock actuator(s) contained in the door latch unit and simultaneously grounds the other side of the door lock actuator(s). This completes the door lock actuator circuit, causing the door lock actuator(s) to rotate a cam assembly in the opposite direction, which then unlocks the door(s). The 12 volts which the central security module provides to the door lock actuator(s) are provided to each door lock actuator from the individual pins on the central security module connector.

Keyless Entry When a remote transmitter button is depressed, it transmits the appropriate command to the central security module as a radio frequency. The central security module receives the command from the remote transmitter through an antenna, which is incorporated in the central security module.
When the central security module receives a command from the remote transmitter, it then sends the appropriate output to control the desired devices. These outputs devices include:

• The front and rear door lock units.
• Central timer module (CTM).
• The liftgate release motor.
• The right and left side turn signal lamp(s).

The central security module sends a signal to the CTM when courtesy lamp illumination is required.
Computer Operated Locks Each front door lock actuator contains a bipolar motor that controls the lock and unlock linkage. The lock/unlock lever of both front door interior handles use linkage to actuate the lever lock switch located inside each front door lock actuator. Each lever lock switch remains in the unlock position until lock/unlock lever of the interior door handle is moved to the lock position. This action toggles the lever lock switch to the lock position. The central security module uses only one electrical input for both lever lock switches. The central security module cannot determine whether the driver or passenger door lever lock switch was actuated. Therefore, actuating the lock feature from either front door will have the same affect of locking all doors. Actuating the unlock feature will not unlock any other door.
The door lock control switches for both front doors also use only one input to the central security module.
Both rear passenger doors contain a rear door lock actuator that controls only electric lock or unlock of the door. Actuating the lock/unlock lever at either rear passenger door will have no effect on other doors.
The panic feature of the remote transmitter sounds the vehicle horn when the vehicle is not equipped with anti-theft. If the vehicle is equipped with anti-theft feature, a separate horn is sounds for the panic feature.

Does it have keyless entry ?
Power Door Locks
The central security module controls the power door lock and keyless entry system. The lock and unlock operation is carried out by supplying ground to the central security module from the door lock control switch. The normal path of the actuators is to ground through the central security module. The door lock control switch will lock and unlock all doors by grounding the appropriate circuit to the central security module. The central security module then supplies power to the appropriate common actuator circuit to lock or unlock all doors.

Keyless Entry
The keyless entry remote transmitter sends a frequency that is received by the central security module internal antenna. Depending on the frequency received, the central security module will lock all doors or unlock the driver door. If the unlock frequency is received again within five seconds of the first unlock, the central security module will unlock all doors.
If the frequency received is from the panic button, the central security module will cycle ground to the parking lamps and horn. The parking lamps and horn will continue to cycle until the panic button is pressed again or the ignition switch is turned to the RUN position.

You can't figure out thing's without knowing how there work , what controls them . In this case a control module .
Principles of Operation

Power Door Locks
The central security module controls the power door lock and keyless entry system. The lock and unlock operation is carried out by supplying ground to the central security module from the door lock control switch. The normal path of the actuators is to ground through the central security module. The door lock control switch will lock and unlock all doors by grounding the appropriate circuit to the central security module. The central security module then supplies power to the appropriate common actuator circuit to lock or unlock all doors.
Plus we don't guess , we test the electrical circuits with a DVOM - digital multimeter or a test light . We use a wiring diagram so we know which part of the circuits to test .

Keyless Entry
The remote transmitter sends a frequency that is received by the central security module internal antenna. Depending on the frequency received, the central security module will lock all doors or unlock the driver door. If the unlock frequency is received again within five seconds of the first unlock, the central security module will unlock all doors.
If the frequency received is for the panic button, the central security module will cycle ground to the park lamp and horn. The park lamps and horn will continue to cycle until the panic button is pressed again or the ignition switch is turned to the RUN position or 2.75 minutes elapse.
Plus we hook up a scan tool that can read codes from the control module , not a code reader for engine codes , won't work ! Need a professional scan tool .Do you know what DTC'S are ? Diagnostic trouble codes !
Central Security Module Diagnostic Trouble Code (DTC) Index DTC Description Source Action to Take B1309 Power Door Lock Circuit Short to Ground Central Security Module Go To Pinpoint Test C . B1341 Power Door Unlock Circuit Short to Ground Central Security Module Go To Pinpoint Test C . B1485 Brake Pedal Input Circuit Short to Battery Central Security Module Go To Pinpoint Test E . B1526 Keyless Entry Circuit Short to Ground Central Security Module Go To Pinpoint Test F . B1629 PRNDL Reverse Input Short to Battery Central Security Module Go To Pinpoint Test E . B2276 Less Than Two Transmitters Programmed Central Security Module Go To Pinpoint Test I . B2425 Remote Keyless Entry Out of Synchronization Central Security Module Go To Pinpoint Test I . - All Other DTCs Central Security Module REFER to Section 419-10 .

• All door locks are inoperative

• Battery junction box (BJB) fuse(s):
  • 8 (15A).
  • 115 (20A) (Super Crew).
• Circuitry.
• Central security module.

• Go To Pinpoint Test C .

Seams you lack the knowledge and test equipment to tackle this type of repair . Your best bet mite be to have a qualified repair shop check it out.
So, without testing i couldn't even begin to suggest what mite be wrong . I would only be guessing , as would anyone on here would.

this is a problem that can appear after your car battery died, cause the car didn't reset propely, so taking the battery out and putting it back in or letting your car die again would do the trick. I tried a lot of reprogramming procedured for my remote key, none of them worked, what did the trick though was simply unlocking the doors via the all door unlock button on the passenger side door, so simple.

Obtain all keys/remote controls. Remove driver's side kick panel/lower 'A' pillar trim. Connect central locking registration connectors (white) - black wire and black/blue wire Fig. 2 . Unlock the vehicle using the key. Program first key/remote control as follows: Press unlock button Fig. 1 [1], then lock button [2]. The door lock should lock and unlock in sequence confirming programming of first key/remote control. Repeat programming procedure for remaining key(s)/remote control(s). Once the last key/remote control is programmed disconnect central locking registration connectors. Check operation of all programmed keys/remote controls.

Your central processor is erratci and givng into wrong commands. Start from exiting one by one from the battery of the remote to the main hand rest., Check for poor connection in the wiring harness specially in the areas of the door hinges where the wires go into the customer control.Also try to find out if any moisture or oil has clogged on to the main Unit.
Hope you have patience.

You must reset your remote control in order for the lock/unlock to work properly.

To reset remote you would:
1)Insert Key in Ignition Turn to Position 1(Don't Start the Engine) for about 5 seconds
2)Turn Key Off and HOLD the LOCK button on Remote while pressing the UNLOCK 3 TIMES
3)Release both lock and unlock buttons you are holding
4)All doors should automatically unlock

And exit the door and lock with the Remote.

there's a fault in it sumwhere

i had a similar problem on the front doors .after taking it to a garage for a quote £ 180 i read into it and there are micro swithches in the locks so with a gentle tap with the hand the door unlocks . hope this helps it saved me the money