Link to BF with detailed instructions https://www.bimmerforums.com/forum/s...-Special-Tools!!!
This only works on Early E31, start of production to 09/93 With SIEMENS 5WK4 027 (65771382905) modules. This module is also found in some E23,e24,e30,e32,e34, and e36, procedure should work for those as well.