could be two seperate problems, the central locking is controlled by a control box in the driver's foot well, each unit has a motor and a switch, the switch connects to ground to unlock and disconnects from ground to lock. the door switch that turns on the interior light works in the same way, it connects to ground to turn on the light and disconnects to turn it off. either you have a grounding issue, which could cause both problems, or you have two seperate issues
