Speed sensor wire o harness??

[cnart]

I have a 1994 318i 4door (made very late in 1994). I am going to install a traffic pro nav system and I am looking for the speed sensor wire. My car has the radio harness (X18126) and on a diagram I found someplace it says that pin #10 (black /white wire) is the vehicle speed signal. Although my old Pioner radio does'nt have a pin at that location to receive it there is a black/white wire at pin location #10 in the harness. Is there any chance this is really the speed sensor signal or is it just wishful thinking. Thanks in advance.