Central Locking Fault

[Grease Monkey]

I've had a fault develop on my central locking on my 2005 D4D. When I unlock the doors and open the tailgate the central locking resets as if there were no doors open. If I open a side door the locking is disabled as it should. Is there a sensor on the door that could be at fault, and if so where will I find it.

 

[Grease Monkey]

Just bumping in the hope that someone can give me some info. I realised that my first post was a bit daft, Opening the side doors disabled the central lockin as it should, but if I only open the tailgate the locking and the alarm are not disabled. I need to know where the sensor is on the tailgate so that I can check it.
I keep on forgetting and I'm starting to annoy the neighbours

 

[grantw]

They are normally just a little push button switch ... and not difficult to locate at all.