1998 BMW 323i VSS

those bmw's are a complete snap to find a vss signal on.  the radios are wired for it.  check the back of the radio for a black wire with a white stripe.  also, if you have a harman system, the wire is a 6 conductor connector at the amp as well that contains the wire.  if those locations are not workable for whatever modules you're installing, i don't recall the BLACK/ white scheme is used on any other wires in the bmw.  if so, the vss wire is small gauge, about 22-24 ga or so, and always always available clustered with the audio harness (or at least i've never seen a 3 series wire harness without it.  hope this helps

ok, so i can't think/type this morning.  i'll try this again.  the vss wire is available on the 6 conductor connector of the harman amp.  the vss wire is part of a sub-harness that contains the 'spatial' switch wire from the console.  if memory serves me from my days at harman, i believe this harness connects to the rest of the harness in the lower IP area.  if you have a non-harman equipped 3 series, you can easily find the vss wire at the radio connector too.  hope that's a little easier to read.