1996 Z3 extra wire under passenger seat?

[96Midlifecrisis]

Where does this go?

 

[NZ00Z3]

It looks like the plug for the passengers sensor mat. Little black box attached to the rear of the underframe.

 

[96Midlifecrisis]

That had all the plugs already attached. The spare plug is not part of the wires in the woven seat wire cluster.