door locking system

  mercedes/e-class/1996-2003

e200 est 2001 central locking not working at all i have to manually lock all doors internal switch not locking key fob flashes as do indicators when fob is pressed alarm system not working either i have changed unit under rear seat with all the pipes on still nothing is there a control unit or relay and where are they? right hand drive
many thanks
DENNIS

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