Some information on the BMW SPMFT & SPMBT modules
I just finished doing a little research on the outside rear view mirrors. The following information is for the E46 Sedan, Wagon and Compact up to 03-2003 with memory. If not equiped with memory the switch block is directly connected to the mirror motors and the modules A212 & A213 are eliminated. After 03-2003 BMW changed the design quite a bit and went to LIN bus from K-Bus. I have included the wiring diagrams for both the Driver side and Passenger side mirrors. The controls modules A212 on the drivers side and A213 on the passenger side are actually identical modules. The only difference is that pin 8 is shorted to ground in the wiring harness to tell the module that it's on the driver's side and to act as the master. Being the master means that it has a switch block connected to it and when the switch block is set to passenger side it sends messages over the K-Bus to the passenger side module. These modules are also refered to as SPM-FT for the driver's side and SPM-BT for the passenger side. In addition to controlling the mirror position they also control mirror heating and tilt down in reverse (passenger side only).
BMW General Module II (GM2) Page
BMW General Module III (GM3) Page