I found a few other posts on the issue, but no definitive solution other than I might need to buy the Resler USB adapter and app.

I connected up an Android headunit last week, along with the 6m cable, all in the back of the car for testing. It powers on fine, but I don't get any sound. The stock large Nav screen headunit is still fitted for the time being, and the screen comes on but no orange light.

I emailed the seller, who said I need to cut and connect the blue (auto ant) wire to the red power cable. I did this, but no joy. I suspect the DSP amp isn't coming on, but I'm not sure how I visually tell if it's on or not.

I don't know if unplugging the stock headunit might help? I will try that tomorrow, but any other ideas?

I've got some photos, I'll attach them when I'm on my computer.