Depending on a model and a manufacture year (not first registration!) there were two different seat occupancy sensor plugs in BMWs: 2-pin or 4-pin plug.
The table below shows which plugs there were in which cars. Pay attention to models coloured in red.
How to find
The plug is situated at the rear of seat. The most comfortable is to slide the seat forward and raise the back side of the seat maximally. Then get into car through the back door. Under the seat there is a black box. The blue plug with 3 wires is fitted on one side and on the other - there are 2 wires that come to the seat occupancy sensor plug. The seat occupancy sensor plug is marked by a red square.
A plug on car has the white end. It has 2 wires: white and blue.
The plug is placed between the middle and the back seat. In order to fit the emulator, you can raise the front seat, get into car through the front door and remove the old plug or raise the back seat and get into car through the back door. The seat occupancy sensor plug is a 4 pin plug, 3 of them are occupied by wires: white, red, brown. On Mini and newer models of BMW the plug can have different colours: white, blue.