Major update for everyone and hopefully an opportunity to clarify the technical side of this.
The ST185 uses a gearbox mounted Vehicle Speed Sensor (VSS) which sends a 'sine wave' signal to the instrument cluster into the speedometer assembly.
The speedometer assembly then converts this 'sine signal' to a 'square wave signal' and sends it to the ECU.
Now, for anyone running an aftermarket ECU but retaining factory instrument cluster, you will still be able to receive the speed signal into your aftermarket ECU.
However, if you remove your factory cluster (or even just the speedo from the cluster) you loose the conversion and pass through of the speed signal.
In this situation (which I am in) you only have a few choices...
- Run a signal coverter
- Install a stand alone speed senor (potentially using the ABS wheels sensors)
So it looks like I have a bit of work cut out for me in order to get road speed displayed on my IQ3
In the below image you can see the flow from speed sensor to speedo (via B8 and B11) and then speedo to ECU (via B9).
Edited by HIRISK, 14 January 2017 - 05:57 PM.