I have a number of strange issues with my 2005 LR3 locking.

I bought the car with only one key and only the driver and front passenger doors lock with the metal key. The remote locking from the key fob button was not functional.
I replaced the battery in the fob, no change, no remote unlocking even though it is now generating a remote signal.

I pulled the 30A fuse (#46?) from behind the glovebox and it was blown, so I replaced that. No change.

When I push the central locking button on the dashboard, all the doors and the tailgate lock and unlock normally.

I can lock all the doors by manually pushing the button by each inside door handle except the left rear door, which will not lock but will unlock using that button.

At present, the only way to lock all the doors is to push the dashboard button to lock the car, then get out and manually lock the driver's door.

So, is this most likely to be a fault in the green / white wire splice under the passenger door sill panel, or the receiver unit in the roof panel, or a door actuator? Hard reset required?

 

Most likely you need a left rear door actuator. The lock button pushes/pulls on a cable which goes to the actuator.

If I were you I would:

1) Do the splice repair, seems like most 05's have this problem.

2) Once that fixes most of your problems pull off rear left door panel and make sure lock tab is actuating the cable properly. If so, replace door lock actuator.

 

Seems like you were dead right, thank you.

The splice fixed the remote locking and I was not the first one in there to do it. It was already badly spliced and taped up, and the rearward cable had detached.

The car now locks and unlocks with the remote fob, except for the rear drivers side door. Replacement used actuator ordered and due in next week.

Update:
New actuator arrived from ebay, was broken in the same way as my old one. I ended up modifying my old actuator by bending a stopping tab (shown by the red arrow) so now all 4 doors plus tailgate lock correctly. I'll try to return the defective replacement unit.




The yellow rings show the broken latches with the broken part still visible in the left unit. Red arrow shows that part I bent leftwards to cause the lock mechanism to still operate with the broken latch.