Central locking diagram is really very simple just laying out the wires to each door and one central controlling circuit, will draw you the schematics in night also will take pictures of motors installed (I forget to take phone down usually when I go to mess up my daewoo
living in flat and biggest hurdle in working on it is it is 3 stories down always).
Meanwhile just check the motor by giving them directly 12 v to there wires green and blue usually one side they should operate outside and reversing the polarity they will operate inside if they are ok then trace the wires they may have a break at some point or 12 V main power is disconnected. if motors and wires are all ok and main wire have 12 V then possible anything faulty in the controlling circuit.