The 24 pin receptacle you are seeing sounds like the OBD2 port and would not be used for a brake controller. You will need to utilize the owners manual or a Saab technician to locate the wires and to determine the functions of those wires. Identifying the wire functions is critical because a brake controller has to be hardwired in since there is no plug and play option available.
The wires on a brake controller are as follows:
white is ground
black is 12 volt power in
blue is output to... view full answer...