(VZ) UART Input for Factory Headunit

[Fu Manchu]

I'm taking a look at all my wiring for the Alpine ILX-702d.

I have the relative Aerpro adaptor harnesses.
On the headunit from factory, there's a wire (Green with white stripe) that goes from pin A1 on the headunit to the BCM.
The only info I can find on it is that it's referenced as "SER_DAT_SCD". I'm going to guess it's "Serial Data xSomethingx".
The factory head unit just says UART on it for that pin. The only UART input I can think of is Speed Sensor input for adjusting sound volume when going fast or slow?

So is this the speed sensor data wire?

 

[Fu Manchu]

This is the pin outs for the factory headunit.

The Alpine harness (one of them) has the speed sensor input. Would be good to be able to use it

 

[Fu Manchu]

 

[Fu Manchu]

 

[Fu Manchu]

Or is the UART input more for diagnostic and security orientated?
I know when a high end interface is connected to my Crewman, it has a code for no headunit info because its fitted with an aftermarket headunit.

 

[slipknot09]

I’m guessing you’ve sorted this out by now, but the UART wire is for the serial data bus. You are correct when you assumed that’s where it gets the VSS, but it would request that info from the bcm. The actual VSS wire is on the GPS connector near the LH A pillar behind the glovebox.
After I put an Android headunit in my car I used that UART wire to give me the memory functions on some VZ Calais seats I installed into my VY Calais, the priority key functions all work as they would in a VZ