The driver's side door lock on the 535i I just purchased would not lock (either manually by depressing the door lock knob or with the key).

I have replaced the lock mechanism and can now manually lock the door so long as I leave the door lock cylinder and power locking drive disconnected (i.e do not connect the link arm to the door lock). If I reconnect the door lock cyclinder link arm, the door will no longer lock manually and will not lock using the key. The power actuator appears to work as it will move when power is connected.

I suspect that the door lock cylinder mechanism is faulty and needs to be replaced. Do I likely need to replace the lock cylinder? If I must replace it, can it be keyed to my existing key set

Does anybody have any insights or suggestions?