[Elantra GT] Central Locking Problem

[Hadas Ofer-BOH006]

Hi.
My Elantra 2003 GL has a Central Locking problem.
Here are the facts:

1.	The Remote Control "operate" on the driver's door only (lock and
unlock)
2.	When locking or unlocking the driver's door manually with the
knob or key the other 3 door do not change their "status". 
3.	The fuse is OK. 

My questions - where is the central locking unit is located and are
there any electraical schematics I can follow?
 
Thanks
 
Ofer