SMFA and SMBF are terms used by BMW to refer to driver's seat module and passenger seat module.
Driver's seat module (SMFA) and passenger seat module (SMBF) activates the seat memory and the mirror memory. Another function of these modules is the adjustment of the front seats controlled by Hall sensors.
When your BMW Seat module fails you may notice symptoms such as not being able to adjust the seats, side mirrors or store seat position in memory.
If you are experiencing problems with your BMW seats first check the seat fuses, relay and even the seat motor.
If you are still experiencing problems with the seats, the next step is to read fault codes from the Seat module.
For this step, you will need a diagnostic scanner that is capable of reading fault codes from BMW Seat module. Here is a list of scanners that can read BMW codes
If any code is showing PRESENT status the problem needs to be fixed before the code can be cleared.
If you can not communicate with your BMW seat module, your module is defective or your vehicle is not equipped with a seat module.
If the vehicle is not equipped with "Seat memory" option, that vehicle will not have a seat module nor Hall sensors fitted. In such cases, when you try to access the seat module, you will get no communication error.
In these BMWs, the seat is adjusted until it reaches an end position. When you move the seat all the way forward or backward, junction box electronics (JBE) recognizes the increased power draw at the end of the rail. If excessive power draw is present, the JBE will switch the seat motor off.