Are you sure its the actuator? I'm having similar problem...my rear doors won't unlock at all with the key fob nor the central lock switch, only the front doors....my first thought would be the central lock switch so I temporarily took the switch off from my other car just to see if it works but same problem. I googled the problem and its all pointing to the GM3 which is very expensive to replace....my plan is to have it repaired, the door lock problems are usually connected with relay failures in the GM3......bmwgm5.com has all the info...you could email the guy and tell him exactly the problem he might be able to help you...