hi guys managed to get the wire
note my legacy is 2010 jdm BR9 which had navigation
after replacing the factory headunit, there's an unused white harness with 4 wires...the light green wire is the one.
after connecting, you need to drive the car at least 40km/hr for the pioneer to change status to connected.
In the multimeter, the wire shows around 5v on motion and 12v on stopping
In my 3d calibration(pioneer dmh-z6350bt), it shows 3d hybrid....now am able to connect my iphone wirelessly to carplay