Instrument cluster - what is this blue wire

[MrBenn]

Went to swap over the instrument clusters yesterday. But the new Touring which is a K plate has this blue wire connected to this green connector on the back of the cluster. Not seen this green part before.
Does anyone know what this Blue wire is for?
Car has no OBC or cruise control.

[twright]

My 1993 318Touring, without the cruise control, also has one.

The green plug is the speedometer output from the cluster.

I've always thought that the speedo output is used by the airbag module, because they don't want the airbag to go off when the car is stopped.

[MrBenn]

Interesting. I didn't know the late model cars came with a drivers air bag.

An interesting use for this wire, it can be attached to car stereos that adjust the volume based on speed.

[Brianmoooore]

There's provision for several blue wires to connect to this green socket, and they all carry road speed information.
I've no idea whether or not it's used for airbag equipped cars, since I've never seen an E30 with them, but I've seen it used for cruise control and radio volume.
I have a couple of late tourings, and both of these have what looks like a BMW fitted radio plug, and both have the blue wire, sothat's where I suspect yours ends up.