Central locking issue

[SrBerlingo02]

Hello there!

Lets me explain the problem... 

I can lock all the doors with the key from both doors (driver & passenger) and also i can lock from inside by the pin locks. But i can open the car from the passenger rear slide door) by the exterior handle.  

Basically, the car is locked but if you go for the passenger rear slide door and pull the door handle all doors open. 

It's a Berlingo '02 1.9.

Many thanks,

[Sol]

Sounds like the sliding door is not actually locking. But it must be signalling that it is closed, or the other doors would not lock.