Yep the best way to re-use factory USB ports is to trace the USB cable up to the BT module, cut it off and use a quality USB cable extension routes to the ISB port at the back of your Sony XAV-AX100.Yeah I have been looking around and posting on a few different threads. I am still looking for a way to use the in car USB port. I am looking to find the Bluetooth unit under the dash and see how the current USB cable terminates there. I might just end up doing my own USB cable to the arm rest and hack the USB port there or just leave it hanging there also.. Right now it is exiting the vent below the head unit because of where i have my phone mount. I found I was putting my phone in the glove box and I was forgetting it! SO maybe even placing it in the center arm rest might not work for me!